Well we wouldn't want the safety to prevent the gun from firing would we?
More than one person has shot their own leg by holstering the Glock with finger (or a holster strap) inside the trigger guard. Bad discipline I know but a pants "safety" IMO - "lemme get this right - you disengage the safety catch by pressing on the extremely dangerous catch (aka trigger)? - sheesh!" .
IIRC the 1911 (or at lease some variants) have a grip safety AND a thumb safety. A thumb safety does not slow down the shooter in the least, and I believe is far safer.