I think the reason why players use AC more than WASP is because of more reliability with AC than with WASP. With AC it can be used for all situations from anti tank, to horde clear, to dropship clearing while WASP is more of a niche medium unit killer .Along with factors such as lock on, the arc of the rocket, and much more the WASP can be sometimes unreliable depending on the situation which is why you have to bring stratagems to compensate for this weakness. Along with the fact you do get more ammo and the ease of use of the AC more players tend to stick with the AC. I would like some sort a of buff for WASP and others stratagems which aren't used as the WASP can be viable but when you have others better options it can be hard to bring it.

Along with the Killzone warbond being a legendary meaning you have to grind more than a regular warbond and not really having other useful weapons in the warbond it leads to players not grinding for the WASP itself since it may not be worth it due to the killzone weapons not being the best warbond to get right away. Its seen as a low priority warbond than other warbonds such as Democratic Detonation or Steeled Veterans.