Well a large number try but inly a few make it. There have been BUD/S classes where no one graduated. If Hell week had lasted ten seconds longer I would have dragged my aching carcass out of the mud and rung the bell. There is no shame or disgrace in deciding that one did not want to finish BUD/S when actually there.
Stay well - Stay safe - Stay armed - Yorktown
"classes where no-one passed" Consistent standards of performance.... that's probably the one attribute of the military that causes lefties to resent it so much.