I don't see much of a point. If someone makes a website and wants people to be able to send money to them for that, a link on that website should work just fine. I'm failing to see the benefit of a HTML meta tag related to that.
> I wish I could click a button to easily send a "tip" to someone who created something I enjoy or to browse other options for supporting them.
I believe most people invested in getting donations already have a similar button on their page.
Plus, to me it seems like this could be ripe for abuse. If you are reading a great post on something, how do you know if the HTML meta tag actually would go to the author of that post, or the hosting platform instead (who sneakily puts in that meta tag on all their hosted content).
With an explicit button, you have to read and acknowledge who you are giving to.