Bib pants & Tour de France



i don't think it's a requirement, but bib shorts are far superior to regular shorts.
 
They don't have too. It is more comfortable with bibs though. They don't slip.

Voeckler wore non-bib cycle shorts during a couple of stages.
 
Oh, they are much much comfier for several reasons (that differ from person to person). But most racers and experience riders agree, bibs are all that. Do a search in the equipment forum, there was a multipage discussion there.
 
Much more comfieee for sure. Plus, if u are out of the saddle and catch yer shorts on the seat, they person behind you dont get blinded by yer pale white ****! and with bibs, you dont have to worry about yer crotch getting all bound up as much cus the nifty suspenders keep everything snug and cozy.