If that were true, they'd still be worth it--even when it's not raining, there's lots of water on the ground from thoughtless fools who can't be bothered to line up their lawn sprinklers properly, and in many parts of town there's lots worse than water flowing on the road! (I remember recently watching a local commuter who is way too hip for fenders, though not so hip he can't ride on the sidewalk, zipping briskly through a flow of fresh piss from the local bum who had just gotten up in his doorway manor....)
Be that as it may, fenders make a bike faster in other ways: for example, I don't need to slow way down for puddles, as the tires can't spray my back and ruin my clothes. Since I wear elegant bike clothing out of my own inventory, I don't want to ruin them, and I don't want to walk around with a wet stripe on my ass no matter what I'm wearing.
That said, I will build the old Eisentraut Limited frame I foolishly bought off a friend last month sans fenders--but just to keep its classic race-bike look intact. (And because it doesn't have braze-ons!) But that will be a twice-a-month play bike. For serious riding, for getting down to the nitty-gritty, I'll take a fendered bike every day. And I do!