Silverfuturist said:"In multiplayer nukes = end of game, end of story"
Join the League or the NQ (no quitters) group and watch how this statement is refuted among strong players.
this.
When I play a multiplayer game(usually over 2-3 nightlong sessions with friends), there is really no point in building nukes. The exception would be if we include AI, then one can wipe them clean if they survived. But PvP pretty much never.
And if you build some and intend to use them: get ready for some hardcore diplomatics with your dear friends. It is funny how quick there is a global alliance against you if you drop the first nuke on a ready-to-go army

my point being: multiplayer nukes = continuation of game, very different story

but back to topic:
I for one have never built a carrier. Not once.
For 2 reasons: if I am playing peacemonger, their radius is still freakishly large enough to defend myself in case of a war. If playing warmonger, newly puppeted cities are your carriers

I play on continent large, usually Immortal and Standard speed. I'd consider myself a decent player, still trying to improve..