...Then again, other, far mightier civilizations are known to have fallen when their capital worlds did (Tkon, Iconians). Perhaps there exists a socio-econo-political mechanism for that, one the UFP is not immune to?
I think the destruction of those Empires may have begun with the loss of their Homeworlds, but it wasn't the single loss that destroyed everything.
Honestly, I did think it was silly how there was only one major Starfleet Academy/HQ and it had to be on Earth. It wouldn't surprise me if there were secondary locations on the other Founding Worlds (Andor, most likely) and we just only ever hear about the Earth ones.