It's been covered many, many, many, many times before.
My personal answer is this....
Can you GUARANTEE that you
will Always have both hands free to rack the slide?
will Never have your hand or arm being held in a deathgrip by a child or loved one?
will Never have a leashed dog on your arm jostling the hand you'd be using to rack the slide?
will Never be using your off-hand to hang on to something for dear life?
will Never be using your off-hand to keep an attacker at bay who got too close before you could react?
will Never be injured in your off-hand so that it's useless for racking the slide?
We carry pistols for the unexpected and because we're Not expecting trouble; that tends to put us 'behind the reaction curve' when trouble does occur.
If we WERE expecting trouble, I think most of us would be reaching for something a bit more powerful than just a hand pistol.
Anyone who's carried unloaded and racked the slide in response to a deadly threat will tell you they always had time to rack the slide.
on the other hand...
Anyone who didn't have time to rack the slide in response to a deadly threat probably won't have much to say, they're too busy being dead.