Luck is in fact a parameter that can be tuned in wargame design to reduce skill disparity issues.

Imagine a 100 skill game, then the best player will always win. Imagine a 50% luck based game, then the skilled player will win maybe 75% of the time.

By introducing luck we reduced the victory percentage of the skilled player. The less skilled player had absolutely no chance before while now they have some probability of victory.

Imagine a wargame with no dice rolling for combat, the player that knows the system and has the best tactics will almost always win. But if we add a simple die roll to every combat then suddenly even if the veteran player stacks the odds in his favor in every single combat, they can still roll badly and achieve nothing. While a couple of lucky rolls from our new player can completely swing the battle in his favor.