I don't think you have to dress them up if you don't want to. Although, I will admit that I wasn't too keen on people putting clothes on their dog when I first bought Maizee, but after learning about her hair condition and finding out that she HAS to wear clothes if she is in the sun or extreme cold, it actually is really fun. It may grow on your friend
Maizee goes outside right now without sweaters on and its about 30 degrees here. I don't keep her out very long since she has no hair to protect herself, but she's fine with it either way, sweater or no sweater.