I guess very few. It is convenient to host many domains on one machine with one IP address. But running on bare IP address would remove the DNS-takedown censorship opportunity, right?
Discussion
I think it has more to do with ownership. Although static IP addresses are not usually subject to change, they still belong to service providers and can be reassigned anytime without notice. Domain names is more perceived as something belonging to the user, although it also has to be registered at third parties and yes, it can be taken down. I'm more a proponent of inalienable public-key addresses like onion services have.