Single place, consistent UI, my credit card details are already there. I can change my card / address for everything in one go. It removes a lot of friction.
I've got my Patreon set up to pay some folks I like monthly, and I can't even tell you who they are off the top of my head, but I decided that I wanted to budget $x towards supporting cool people and it's been charging me in the background ever since. Meanwhile, I can barely remember to pay my voice teacher every week and I go there in person (well, not anymore) and sing for an hour.
In addition to what lmm mentioned, giving to patreon usually comes with some sort of perk or special content, and it's also a subscription by default which I imagine isn't the case with a donate button.