Internal extractors have a little more gripping power for removing sticky or out of spec cases. If a chamber is dirty or the case decides to stick external extractors can esily pop off the rim.
In the case of 1911 the extractor was designed as an internal one to meet certain criteria and be reliable under even the dirtiest battlefield condition. JMB knew what he was doing.
"Gun control: The theory that a woman found dead in an alley, raped and strangled with her panty hose, is somehow morally superior to a woman explaining to police how her attacker got that fatal bullet wound." — L. Neil Smith
The problem with being stupid is you cannot simply decide to stop doing dumb things...
"I crapped my pants to avoid the draft!!" -Ted Nugent