For those who don't, it's a UX nightmare, because the standalone info viewer uses a specific, relatively ill-surfaced subset of Emacs conventions for its navigation commands. No one who doesn't use Emacs can be expected to know any of these. Even those of us who do use Emacs often don't know any of these. It took me more than half a decade of daily Emacs use to discover them.
And even leaving that aside, Texinfo is fundamentally broken in a really disappointing way: the source includes almost no semantic information whatsoever - imagine HTML with no whitespace squashing and no tags except <br> and <a>. Worse, there is no consistency whatsoever among different authors on what structural conventions to use. It's therefore somewhere between very difficult and nigh impossible to implement anything like this rather nice colorization of manual pages. There are a couple of Emacs packages which try to do that, but while they do the best they can, that best isn't very good - and, of course, they're only useful if you use Emacs.
Honestly, it's a really frustrating situation. Texinfo manuals, especially those from the GNU project, tend to be much more detailed and complete on average than manual pages, which makes them an excellent reference for cases where the aide-memoire style of a man page doesn't convey the context you need. But the info system is practically impossible to use unless you're very familiar with Emacs, and even when you are, it's still almost impossible to make info any more useful than plain text would be.
Given the age of Texinfo - older than three-fifths of the developers who answered Stack Overflow's 2016 survey! - it's not terribly surprising that it was born with flaws like these. But after thirty years, it is somewhat surprising that those flaws still exist.