So business deals are beneficial to both parties, just like buying/selling an option between two parties is beneficial to both of them? No one loses? Both of them win? Both make money? Both are happy? Both have improved the world and their own lives? Maybe Citadel also wants everyone to make money and share their success?
Maybe you don't realize this, but when I sell you an option, I want to make money - and unfortunately this means that I need you to lose money so that I don't lose. When market makers buy my option, they also need to move the market in a way that they and I don't lose, but someone else may.
My scam comparison was extreme just because I needed an evil chuckle today for my selfie (or mirror reflection as you've put it), but trading is nothing like business deals - it's a championship, it's ruthless and only the best ones win - traders want excitement and success, they want to be best and they want to be Muhammad Alis or Citadels of trading, not some guy signing some business contracts and live happily thereafter. It's a fight and they're here to win, otherwise they indeed do something else like signing some business contracts and stay away from the fight (trading).