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.

For 10 years I’ve had an automatic $2 monthly PayPal payment sent to a podcast I enjoy.

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.

It's the same thing that PayPal brings to the table when any website could just have a credit card form.