I've always thought it was fine, since the reality of it is that today most people dont know what to wear unless they're told. Even if you know what's correct, you're still unsure if you will be completely out of place dressed appropriately and have to deal with a very angry bride.
There is no bride or groomzilla for my wedding, but my friends/family generally like to be more formal for weddings and it will be after 6.
I agree. It may have been uncouth at one time, but at this point, you pretty much have to clarify.