Most people who make their games free have a Patreon. So, they're not releasing their games for free because they're generous, it's because they are getting paid for working on their games.
If a person releases their game for free, and has no Patreon, it means this person cannot gain money from their game because either it's a very basic and very short game, or because they're not popular enough.
It's sad, but it's true. Do not think they're just "generous", there are a lot of things to take into account.