My english is not great but actually i ment what gives value to currency in general.
Someone or something must pay the difference in speculation(car sales or stocks or fliping housing)
all those specialists need food and other resource to continue hustling.
Human, robot, automation , whatever is moving resource out of mother earth, or producing something out of it .
Other than evaluating stocks or flipping cars , houses etc.
Its bad example but IMO if noone would be actually moving themselves for currency+all automation would be stopped.
And everyone started speculation tomorrow.
Currency would be paper, not even great toilet paper.
Or bits in computer ,as useful as score in videogame.
Soon the computers would turn off due to no electricity, unless robots/automation would have failsafe automated maintance of automation.
Car has to be built,maintained etc. Speculation does not directly add that type of physical value IMO.
To my knowledge liquidity is only useful for other specialists who are on opposite side.
But can price go 2 opposite ways simultaneously benefiting both opposing parties?
If its spread widening, then middlemen benefit.
It does seem like zero sum game in that sence.
Also investors can be balancers , adding money&motivation where its needed.
Gaining on correct decisions.
Gain might be others loss at least with human labour.
With robotics and automation it may be harder to classify loss if little maintance.
Rigging the playing field is also popular.
https://en.m.wikipedia.org/wiki/Lemon_socialism
Privatizing Profits And Socializing Losses seems like 1000+year old zero sum scheme.
Your English is actually great! Especially, if it isnt your first language ! If I have trouble understanding your question I will try and clarify before answering. It is okay and good to ask these questions, mankind has probably been questioning purpose and meaning since he first was able to think. unfortunately sometimes people who we seek guidance from, parents, professors, aunts & uncles, bosses, higher ranking superiors, random dudes on an online forum dont always have the answers. But I will give you my perspective, and you have to make your own decisions based on your own reasoning.
ON CURRENCY*
To be fair I have no idea (or interest in the currency market). But to answer your question on, what gives "value to currency".
Imagine you are a King, there is an open market in your Kingdom where people come to trade. Many of your subjects (both those with much and those with little) come to you complaining, saying that if you could provide a coin it would make their transactions not only easier but much more fair. They even mention to you that the Babylonian, Persian, & Roman King has been doing this for centuries. You are a well respected King, and people feel safe living under your rule. The people of your Kingdom love red roses, you guarantee that for every coin you print with your imprint on it you will offer a dozen red roses for each coin that is brought to your "house of coins" (later becoming a bank).
YOU HAVE NOW GIVEN "VALUE" TO THIS CURRENCY. (Ofcourse, if your grandson is not as competent a ruler he could easily destroy this value, but in effort of keeping this reply shorter I will leave that part out.)
So now you have moved the goalpost :O). the original question was "are markets a zero sum game", however I will still address the "speculation" & "liquidity" questions as well. Also, earlier I asked you to clarify which markets, it seems in your latest post you are mostly referring to currency markets?
GENERAL MARKETS, LIQUIDITY & SPECULATION
Instead of cars, (or horses) lets think of t-shirts for example, we can complain that the t-shirt vendor is "hustling" to make a profit. Of course, that t-shirt vendor also has to invest resources (currency) to buy enough t-shirts from the factory (which has to invest resources) to buy the materials from the farmer (which has to invest resources). Also, this t-shirt vendor, has to invest either his/her time or more resources as well as taking a risk that nobody buys his t-shirts, to sell to you which only want 1 t-shirt, you are well aware of this vendor making a profit off of you but seem completely content with avoiding how much energy was invested to get you that t-shirt at a price where you would be willing to buy it? (this t-shirt vendor provided LIQUIDITY, he also SPECULATED that he could make a profit)
Flipping houses, although may seem very simply and easy from Hollywood produced entertaining television shows.is a very, very, tough, business, it is actually very risky, and if you dont know what you are doing you can lose your shirt, and owe investors money just as easily as you could in the stock market. People, from the outside may see someone post numbers of making +25k from a "flip", but have no idea how much energy, management (have you ever managed a construction site???) and RISK the "flipper" was putting into this project.
Again, we are moving the goal post a bit here, however...
Both speculation & liquidity is loved and adored by ALL participants, there are of course "bubbles" which are ignited by human greed, and it is not until after this "bubble has burst" that those who greedily chased will cry foul.
In the housing market, liquidity & speculation is great and I will explain to you why. if you are a buyer. You could in theory go door to door, and ask people if you could buy their house. You can make them an offer and keep going until you find a house that you like and the seller is willing to not only sell, but sell at a price you are willing to pay. Good luck with this approach, of course there is another approach (a market) where people put their sweat,energy, and $resources to providing you with a much easier way of doing this transaction. They have *SPECULATED* & are providing *LIQUIDITY*, with out such your task of buying a home would be much more difficult.
So to answer your question, liquidity is beneficial to both parties. both the buyer and seller are benefiting from someone elses, RISK, LABOR, INVESTMENT & TIME.
***
You can study the Tulip Bubble from 1637, to get a better understanding of markets, and bubbles and how Speculators and those providing Liquidity are the ones that get rekt when the bubble finally bursts.
Again, I am not into currency markets however if you want to get into currency trading you should do much more research. I am not aware of the market but from BS advertisements and what friends have shown me, I think most "traders" are really just making small bets only within their brokerage, not all brokers are BS but I think most traders brokerages are likely just taking small bets, this is not good or bad but they arent really "currency traders" despite what they may think in their imagination.
Lets say for example, you are the director of the central bank of a country. You do not have much faith in your countries currency, should you SPECULATE and trade some of your currency to something that you feel will hold its value better? You traded your worthless currency for a stronger currency which you are now holding in your reserves. Who won? who lost?