A twofold problem:

• Payment processors and their crusade against adult content
• Steam, which is technically not a monopoly, has the power of one due to its sheer size - thanks in no small part to the competition shotgunning itself over and over. GOG is the only one that isn't actively hurting itself every month with stupid decisions, afaik, but its reach is tiny compared to Steam.

Steam rejected Future? No Thanks! again for the reason: ‘Contains sexual content that is explicit or graphic and is intended for adults only,’” Pedercini tells me. “They say they can't specify the reasons or point at the content.”

Steam's review process being completely opaque and unhelpful also sucks.