but, by the time that determination is made, the address in question will not be used again. Blocking the address at that point is just a waste of time.

It’s not. If everyone keeps them blocked, it will make ISPs who sell residential proxies shoot themselves in the foot.

Bright Data offers a “free” VPN service; all that is needed is for the user to give Bright Data the ability to route traffic through the user’s device — to become a part of the company’s residential-proxy network, in other words. Every phone or other device that makes use of this VPN becomes yet another endpoint that will be used to attack web sites.