- ISPs leverage DNS blocking to censor
And blocking the IP address of the site in question, as well. That’s why so many “illegal” sites jump around IP addresses like a flea on a hot griddle. They’re trying to remain accessible whenever the ISP prevents direct access.
Because if you block the IP address, blocking DNS is superfluous and performative – it’s just window dressing for better optics towards politicians who don’t understand tech. DNS censorship trivially bypassible by using custom DNS servers that aren’t affected by the censorship, while IP blocking hits everyone who is under that ISP regardless of their DNS settings - they need a VPN to bypass IP blocking.