If he doesn't display a weapon and you shoot him, you may have just shot an unarmed man (the old finger in coat pocket gag).
Shouldn't bring a finger to a gun fight.
Besides, if he wasn't going to shoot and you pull out your gun and yell FREEEEZE, he might decide to start shooting.
If you've never been a cop or soldier, you have absolutely zero business trying to control such a situation with voice. Sorry, but you don't. Cops, and many soldiers, HAVE controlled a number of situations with voice, and know how to use inflection, body language, etc, to help guarantee compliance.
Bad guys know this. Bad guys recognize this.
Bad guys do not want an off-duty cop/soldier as part of their robbery pool because they KNOW off-duty cops/soldiers WILL shoot their ass dead when defending themselves and the group they're a part of.
And if you pull out your gun and the bad guy decides to pull out HIS gun, you'd damned sure better have made the decision the nano-second you pulled your weapon that you had every intention of using it and using it lethally.
Again, if you've not been a cop or soldier, you have no business using your weapon as a persuasive or negotiating tool.