A single shop keeper in a remote town may be providing a 'convenience' service to his community but he can fix prices for a big profit.
A second shopkeeper who sets up in the same town selling the same goods is not providing an additional service to the community in regard of convenience, but he is providing competition and lowering prices.
A third/fourth/fifth.. shopkeeper will provide even more competition and pressure on prices. Only the most efficient and best run shops will be able to survive and the others will go out of business.
The same thing occurs in trading, the more traders the more efficient the pricing of commodities and stocks. We provide the same service to society as other businesses and we risk our own capital to do it.
Any trader that cannot improve market efficiency and price discovery in a highly competitive market wont be able to turn a profit and will go out of business. Losing traders do not provide a useful service to the markets. But the consistently profitable ones do.
