I concluded that the AD&D version of the "weapon vs. AC" table was interwoven with the variable weapon damage - some weapons have apparently sub-optimal damage dice, but when used with the "vs. AC" table are a better choice for doing damage to a heavily armored character. If you don't use those tables, there's no mechanical reason to use those weapons. I don't have the tables to hand, but I recall it being an issue with piercing weapons such as war hammers, military picks, and stabby polearms. Probably crossbows, too.
FWIW, TSR fixes this ;)
Having returned to D&D after many years, I've come to realize how the rules I previously ignored changed the flavor of the game. For example, as a kids we hand-waved encumbrance, food, light source tracking, etc. It just didn't seem important or fun. Now I realize I missed a significant aspect of the game by ignoring those rules. I've come around to the opinion that it's not really D&D without the resource management.