Devs could release the games anywhere and receive the donations through Patreon, but most devs approach the release as a sale and not what the Patreon is about: donations to support an artist's work.
Most people give money only for support, not because they have to, just to get an early release or previews.
I know some people give money as a means to influence the dev, but still, most people do it for support when they could just get it for free.
On the other hand, Patreon site is just shameful: they sholdn't have that name, since patreon is an institution from the renaissance to support artistic freedom and creativity, not to censor it.