[A26B]

The dipstick seals can be accidentally pushed into the crankcase during dipstick install if it comes off the dipstick when it's removed, especially if the mechanic doesn't know it's there. I've had a couple of calls saying "mine didn't have one" or it "disappeared cuz I can't find it." O-rings would be easier to lose that way, but beats the heck out of nothing. If the bottom of the dipstick was "flared" maybe the o-ring would stay on better when removed again.

One note: I don't think the seal ending up in the pan is the end of the world.... probably won't hurt anything since it's below the windage tray & the pickup screen will stop it from getting into the pump.