The one word answer is: culture. The culture of academia — and indeed many other areas of life — has a variety of rules placed on self-promotion and naming. These are, in many way, arbitrary, capricious, and often illogical or unreasonable, but that's just how culture is. It serves various functions, some good and some bad.
The general rule is: complimenting someone is an honor, while complimenting yourself is usually frowned upon. The cultural mores are that you should be concerned with other people's opinion of you and work hard to win their high regards, but you should be humble and uncertain of your own personal values.
This is partly due to a myriad of psychological mechanisms, like the fundamental negative bias (people are naturally better at spotting and remembering negative things), attribution bias, illusory superiority (everyone thinks they are above average), tactics to combat free-loaders/loafers/cons, and vested/conflicted interest.
In short: we are highly skeptical of people who are trying to tell us how great they are. Also, naming things is hard, at the same time as having something named after you is considered an extremely high honor — a truly grand compliment.
If I said, "Man, that Brian guy is really an amazingly great person" or if I discovered a previously unknown kind of rock and named them "Brian rocks", there are many people who would immediately have the urge to punch me in the face.
It is further generally recommended that you avoid doing things that make people instinctively want to punch you in the face. And so it goes in academia. You are free to ignore it and name a tower after yourself or try to place your own name on a discovery, but you should just be warned that some people might not react well to this.
Ultimately, it's just a weird social truth: it's always better to have people compliment you than to have to do it yourself. That's not to say you can't toot your own horn (especially when no one else seems to want to), but it's way better to get yourself a shill.
Man, that Superbest guy asks great questions...
Note: Not all cultures are this way. Indeed, in business it is generally accepted that you can name the business or product after yourself all you want, and self-promotion is often actively encouraged with far less limitations. This is, one might imagine, an area where business and academia don't always see eye to eye.
