>Right now, after pirating it, I have to find the author's patreon / something and contribute some money that way. It shouldn't be this hard to give someone money
Why not just buy the thing you are pirating? That would seem to be the easiest way to give someone money.
The thinking is the sold product is the inferior product than the pirated version and so rather than reward the people making it worse (Amazon, mostly), trying to reward the person who made something you want in the first place
Because significantly less of the money you pay goes to the person who wrote the book.
To quantify that: If the author has self-published on Amazon, 35%-70% goes to the author. (70% above a certain price threshold and assuming the e-book is exclusive to KDP) If published via a publisher, the author is more likely to be getting 10%-15%.