I see what you're talking about and honestly I suspected you'd bring up this seeming use of names as improper grammar relative to the sentence structure, the thing is if you think about it this way:

What question do you ask when you want to know a person's name? That's right, it is:

Как тебя зовут. That bit is very imprortant, you don't ask: Кем тебя зовут or чем тебя зовут, those two questions are a completely different matter, you don't ask one of those to ask for a name. The former is more about "what nickname you have?" or "what "other name" people call you to distinguish you from others because of your accomplishments, quirks or antics or whatnot", like in Александр Невский or Пётр Великий or Иван Грозный. The latter is like by what means or object people call for you, like a horn for example.

Based on that you can even say that names creep into adverbial territory there and adverbs don't change in Russian as you well know. I'm sure all the grammar nazi out there are sharpening their swords and cleaning their guns right now but it is what it looks like and explains a heck of a lot of things You can even have a little pun out of it:

- Как тебя зовут?
- Громко и чётко!