Plain and simple: names are your record of accountability. If you, or anyone, is a horrible player, you should not get the opportunity to pay to dodge your bad rep.

Conversely, if a good player quits you (or whoever) should not get the opportunity to impersonate them and inherit their good rep.

There's really nothing else that can be said here, much as some would like to do this due to poor choices, the fact that allowing name changes allows players to dodge accountability of the rep they get will make sure this never, ever happens.