Earlier quoted context omitted.
I have the same process on my site. The reason is that it is such a risky operation that you want to have a human in the middle as a safeguard from accidental deletion. Account cancellations and so on are automatic of course, but anything that can’t be rolled back requires human input.
It guess it's not hard to put a deletion timer and send warning emails before actual deletion. Not every service out there requires you to send an email to delete your account.
It is possible, but it is expensive and risky to do it right. In my case there were perhaps five people that requested data deletion over the span of 8 years the site was working. Features that are so rarely used you don’t automate.
Granted, I could’ve added a button that would send the e-mail automatically. It just honestly never crossed my mind - will implement it in future sites :)