Fencing breeches should be worn, not only for the neat image they present of the fencer and the club, they are also regulation equipment that must be worn in competition.
In training sessions, track suit trousers are the alternative NOT jeans as they allow more free movement.
Breeches come in different weights (measured in Newtons of force) offering levels of protection. 350N is the current minimum for club use. When buying new, get a pair of 800N breeches.