Patreon access unlocks a lot of new content. This includes around 200 bonus costumes and clothing items, a unique event with an NPC in the Church of the Patrons, bonus quests, hidden scenes featuring the ending and pregnancy, as well as the ability to unlock in-game content faster.
And that's not even counting the benefits of subscribing on Patreon website.
I've reached one of the quests that requires cumming in or being cummed in. 1st one appears at HR5. If this can't be unlocked through regular playing then it won't be done.