Re: How is this any different
Your plan will almost never work. Let us count the ways ...
* Many web sites share an IP number amongst more than one web site, e.g., example.com and example.co.uk could be different sites both served by a server at 1.2.3.4. If you access the server using its number it won't know which site you want.
* Especially since we're talking privacy here, the sites will use HTTPS, requiring a cert for the address visited. The server will have a cert for the various DNS names it hosts but almost never will it have a cert for its IP number. So accesses using your technique will be totally insecure and vulnerable to interception and rewriting.
* Even if there was only a single web site on an IP number, the server will want to appear on the web as a single site. Not only does this simplify configuration and management, it avoids diluting the site's web presence across what search engines consider different sites. So requests to example.co.uk, www.example.co.uk and 1.2.3.4 will all be instantly directed to the site's preferred domain. This will cause a DNS lookup even if you typed 1.2.3.4.
* It can actually be difficult to configure web servers to respond identically to queries that use different names. Even if the server allows you to access content without redirection at both example.co.uk and 1.2.3.4, the content you see will often vary.