I don't think it's necessarily motivated by a desire to have "charismatic" or "exotic" sounding names, as much as a desire to avoid having names that sound incongruous with the fantastic environment.
Much fantasy is set in a different universe from our own. The culture depicted is usually at least somewhat different from any real-life culture. And we expect people in different cultures to have different names. When we translate a text describing something that happened in another culture, we usually don't translate names, we just transliterate or transcribe them.
The same applies to historical fiction like "The Clan of the Cave Bear". We know that names like "Henry" and "Alice" are associated with particular modern real-world cultures, so it would be weird to encounter them in Paleolithic Europe.
That said, some fantasy has cultures that are very obviously modeled on real-life cultures, and in that case using real-life names is not that jarring. You mentioned "Daenerys", but George R. R. Martin actually uses a lot of names that are clearly based on real-life European names like "Eddard", "Catelyn", "Brandon" etc. This works since the culture they live in is clearly based on medieval European cultures. Martin seems to like to use unusual spellings, but I don't think this is really necessary.