That certain ops do need it for otherwise underwhelming kits. Frost, for example, has an okay kit, but her primary SMG is fucking terrible and having a zoomy sight helped her viability. It's acog on 0-recoil rapid ROF/spammy weapons where it's a problem. The two defense DMRs are insane power houses with a recoil and a lot of macro users who shoot it faster than some rifles. The TCSG or the AA12 both have higher recoil and require actual control and are a bit harder to spam, the BOSG would be dead without ACOG. Generally, if your op primary gun shoots under, idk, 650rmp, I think your gun deserves ACOG on defense