Why do some Sikh men keep their head hair intact but still trim their beards?
Those Sikhs who cut any of their hair do so because of outside pressures. Society and/or family are affecting them. They have forgotten, or perhaps never understood in the first place, their identity as Sikhs and the purpose behind the practice. Sikh men who trim their beards (or hair) may not have chosen to be baptized in the Amrit Ceremony. A baptized Sikh commits to observing the Rehit (code), which commands one to keep their hair uncut.