And making DDoS-attacks nigh impossible to IP block.

Residential proxies are in many cases at least shady, both on the side of who uses them and for what and on providers that are often not above using dark pattern to hide them in some innocuous app for a smart-whatever that silently runs a proxy on a unaware user's connection. And in many places in the world if illegal stuff in done using your connection you are liable, regardless if you knew about it.