In the traditional multiplayer space, the players with the best stuff and most progression are lifers. Those real addicts: The people who are online all day every day, whenever you sign in. A lot of them are kids, and I used to be one back in the day. But as a full-time employee with a wife and a kid, I can't ever compete with that.
Pay-to-win games give people who work good jobs a way to compete: If I know that an item it'll take me three weeks to grind out will cost me $20 to buy outright... I make more money working in real life, so why not buy it in-game instead of wasting my time grinding.