You are correct, gloves simply add warmth or protection(sometimes both)But.....believe it or not some folks out there need something more specific than that. A Tactical glove would be a glove designed specifically for military or police use and in this particular case they are designed to meet certain specific criteria based on that intended use.
-Slim fingers for better weapons handling.
-Kevlar weave for personal searches where someone may have sharp, stabbing objects on their person.
-A higher flash resistance for flash burn protection from explosions(IEDs being the big one)
-Extra protection to the knuckles.
And yes, if you wear a black uniform you can ever find them in the same color without resorting to painting them.
-The CAG 1 is not designed to keep your hands warm either. Thought I should add that.

Yes , tactical may be a term often thrown around at each and every corner to increase sales, but I am very certain everyone here happened across the term "tactical glove" once or twice and could draw the conclusion they are not your everyday run of the mill gloves but are designed to fit a more specific role.

Oh! BTW, You should tell the next Police officer you see in SWAT gear that you think he simply paints his gloves black for the sake of cool guy points. You may learn first hand (no pun intended) why they have hard plastic knuckles.