You raise a good point. However, several incest games began before Patreon imposed their restrictions. Also, for a long time it was the only convenient place for developers to sell their games. It still is, if the rules are complied with. Which is why developers who switch their incest games to other hosts (like Mr. Dots) still maintain a page on Patreon for their non-incest games, in order to maintain that revenue source. Plus, many developers find the convenience of Patreon so alluring, that they work out patches for their incest games, or just hope they can sneak by without notice, which worked for this game for a year and a half... and for 10 months since it actually became an incest game.
Patreon is probably the most accessed site for subscribing to porn games. All others are relatively new and unknown to most. Thus, you will hardly find a game here on F95 whose developer does not have a link to a Patreon page, be it an incest game or not.