onlyhuman said:
Doesn't that mean you have a practical reason, apart from the snobbery? Having said that, I don't know why it would matter less if the aluminium frame got wet...
Haven't you heard? Carbon dissolves in water.
OP: In winter there's a lot more dirt and grit on the roads which accelerates wear on your components. A lot of people have very expensive kit on their good bike so the cost of replacing a cassette, chain, BB etc. can be quite high.
Also, some purpose designed winter bikes will take full mudguards which normal road bikes won't.
Matthew