Right!
It'd take me at least a minute or two to dig my laptop and cords out of my bag, much less a gun, which would inevitably be at the extreme bottom of all of my other useful crap because I never use it.
Then again, if you did yell, "WAIT!" and started rummaging through your bag I wonder if the other guy would stop and think "whoa, I wonder if he has a gun , or something..." and high tail it out of there.