I think the purpose behind the convention is:
* put things where people can find them
* let people know the "correct" names
To fulfill these 2 principles, we several various naming conventions, as well as the
redirect feature and disambiguation pages.
For English speakers (our target audience), Roma means gypsies and Rome is a city in
Italy.
Of course English is not the only Wikipedia language. The Italian Wikipedia (when and if
we get one) will call the Italian city something else (like 'Roma').
We can't yet write a single article with multiple translations, so we have divided up
the work into several related 'pedias. But each 'pedia tries to put things where
people can find them, as well as let people know the "correct" names for them.
Ed Poor