Most free to play games have an in game currency that people pay money for, this model provides developers a consistent amount of revenue from their games, that in turn can go to paying employees and creating more content for a game. This model allows good developers to continue making content for a game, while the bad ones are left out to die. This also provides an incentive for developers to provide quality content, since they don't get paid based on download, but based on the people who like the game, buying what they want to buy. This also allows developers to experiment with their game and regular and fast updates. Take for instance Paladins by HiRez Studios, and Overwatch by Blizzard Entertainment. Early on, Paladins was the free Overwatch. However, Hirez had incentive to make their game better than it was, by consistently adding more heroes, creating an item and card system for those heroes, as well as consistently bringing in new cosmetic items and balance changes, and since Paladins was free to begin with, people didn't value what they payed for as much, meaning the developers could changes and tweak things without major uproar, and the addition of the card system for paladins created the option of having different play styles for the same hero, and thus allowing the heroes to become more accessible, unlike Overwatch, where each hero had a certain play style to match, a small change that was allowed by the no strings attached model of a free to play game, as well as improving the availability by making the game free (Duh). When people buy a new $60 game, they feel some sort of incentive to play it and justify their spending money on it, and again going back to developer incentive, people are less likely to leave a game they paid $60+ dollars for, but when people play a free to play game, if they leave, the developers feel more financially, since all they are making money from is the players consistently buying from them.
Thank you for reading, sorry if this was hard to follow, this was my first post and i am willing to take advice on what I could do better, so please feel free to comment on what i could do better