The DNS resolving process ultimately relies on root servers located in the USA for most extensions (.com and .org root servers for example). Even if the IP addresses of these servers are cached by local DNS resolvers in my country, relying on domain name and root servers is sort of a single point of failure, and bring well known weaknesses (DNS hack, DNS poisonning etc...).
Let's say I have strong confidence in the ISP that allocated an IP address to my house/workplace, or even that I own this IP address, I know I'll always be reachable at this IP address, and I have registered for a SSL certificate for this domain.
Considering this (that you can trust IP address and certificate), is it more safe to rely solely on IP address (over SSL) to host a web service, and therefore do not register for any domain name?