The POST verb exists, there's no reason not to use it to ask a server to delete data.

In fact, there are plenty of reasons not to use DELETE and PUT. Middleboxes managed by incompetent security people block them, they require that developers have a minimum of expertise and don't break the idempotency rule, lots of software stacks simply don't support them (yeah, those stacks are bad, what still doesn't change anything), and the most of the internet just don't use the benefit they provide (because they don't trust the developers behind the server to not break the rules).