First of all, vaginas don't become "loose", they are a muscle. They stretch and elongate when aroused and then quickly go back to normal during the plateau stage of arousal.

Secondly, this doesn't mean your vagina is numb. They are a marketing gimmick. I've never felt them, and I doubt very many women can - and even less than that probably find them *more* pleasurable than condoms that don't have them. Also, the first 1/3 of your vagina is the area with the most nerves - and in my experience the ribbing etc is further up on the condom than that - so it would make it even harder to feel them :)