Pretty much it's because California and New York like to broadcast themselves as extremely openminded while also being extremely prudish in many ways. Patreon and its financial facilitators are pretty much headquartered in these two locations.
Ironically, they censor this type of thing while allowing all kinds of corruption and
actual problems to persist. The shit Hollywood gets up to is OK, but heaven forbid we allow stories with computer-generated characters to have incest in them. The massive homeless problems on the streets of Oakland, San Francisco, Los Angeles, San Diego, and elsewhere are apparently absolutely fine, but holy shit we can't allow any high-school-aged relationships to be fictionalized with modern artistic tools — even though portrayed high school sex by films is completely kosher.