They don't strip, or at least it would take a tremendous amount of torque to strip them. My experience has been that the driver strips before the head does.
That stripping the driver before the screw is a feature. Heads come with every box of screws I buy, and getting out ruined screws is far harder than replacing the driver.
Happens with the better ones as well, it's just a matter of setting the torque limiter of your screwdriver/coordless drill to match the job. Sometimes takes a few mistakes, but it's safer to start with a low setting and adjust up until you have the right torque for the screw.