He most likely does , but it is easy for a guy in a hurry to use the incorrect hex ..I always keep my set in seperate boxes just for that reason. If the correct one is used [ and it is not a POS one] , they are pretty hard to strip out.
Another preventive trick is to clean out the hex of dirt/grime before inserting the allen so it gets full depth seating........ then they are very strong and seldom fail. The deeper it seats , the stronger they are.
Another is they have ones with a ball end for offset angle usage , but these should not be used on bolts that are really fastened...bests to break them loose with a straight , short, well seated, correct allen bit on a socket.

..and a trick for removal of a stripped one when all else fails is to place a nut on top and weld up the hole, then use a socket the size of the nut..that is a last resort, but comes in handy sometimes..[ good trick for sheared off studs , too...]