I'm guessing it would be to make sure your hand isn't on a gun in the pocket.
I didn't see the officer with his hand on a gun until the refusal to pull a hand out of a pocket.
What is the specific, reasonable, articulable suspicion that the man had a gun in his pocket? (Or, that the suspected gun in his pocket was unlawful?)
As for "orders from a police officer".... If he orders me to shoot someone, no I'm not. If he orders me to take my hand out of my pocket.
I'll ask the same question: if you think that a request to remove a hand from a pocket is reasonable, what other things are reasonable? If a police officer has no reason to bother you in the first place, why is ANY request - especially when issued as an implied command - reasonable?
If he wants to search my car, I will let him, but in a calm voice inform him I do not consent to a search.
If you let him merely because he "wanted" to, then you just consented. If he has probable cause, he doesn't need your consent, even if he asks for it. (Maybe that's what you mean?)