>>31073439Most Pokemon with weak armour almost always want to run their other ability.
The ones you mentioned especially. Skarmory runs Sturdy so it can set up hazards on a counter, Kabutops and Omastar are faster without taking damage and lowering Defense under rain with Swift Swim, Crustle wants Sturdy so it can guaranteed Smash up, Garbador wants Aftermath, Vanillux just got Snow Warning, Magcargo wants Flame Body to get burns and Mandibuzz loves Overcoat since it's bulky as fuck and doesn't take chip and is immune to Power moves.
Weak Armour isn't very good after the buff, and the Pokemon that have it also have a better ability available.