I guess the reason for rolling my own webmention receiver is that I don't want to rely on services I don't manage or pay for. Now, an argument could be made that I'm putting everything on Netlify, so my eggs are all in their basket. My counter to that is that the functions I'm writing fairly portable. All I'd have to do is wrap the functions in a little server. So, the important part is to own the logic! Of course, there's also the fun part of reading a spec and implementing it.