Because sometimes you're greatly penalized for doing well as the random number generator produces QUITE scewed results (the "fixed dice" syndrome)
Example: Saw the border of a well-positioned barb city. Attacked w/ 1 cat and 3 maces (all full health). Moved in to see that it was only defended by two archers, no upgrades, not on a hill. SHOULD be overkill.
After the cat sac (which actually should have won, it's power was greater than the archer), the first mace attacks. He's lvl3 (C1 and CR2). His power would then be 12.4 vs. what would have been 3.7 if the archer hadn't taken coll damage. Despite more than tripling the power of the already damaged unit, he loses. The second mace attacks the other damaged archer. He's only lvl 2 (CRII) and, alas, only barely triples the power of the unit that the cat directly attacked. He loses as well. The third mace, lvl 1 w/ CRI, tries to clean up; both archers are on their last legs and their power is half of the maces (or would be if they weren't dying). The mace loses on his first attack.
I don't consider reloading to fix this gorilla math cheating. When a unit loses to a unit with 1/5 his power, reloading actually removes a cheat, not create one. As for the modern armor comment, reloading is used to remove the modern armor dressed as an archer, and I don't see the comparison of adding one in. The problem being addressed is that, even if we did add in the modern armor, it'd lose to the archer anyway.