That seems an awfully kneejerk and Gen4 centric view. Next you'll be saying Fling on Gliscor is useless because "it only works once".
With Evolution stones, Balloons and the like running around, or new powerful abilities requiring item support, a disruptive move like Trick suddenly sees new viability - especially it's damn near impossible to reverse the effects of, unlike with regular status. Even something as simple as taking Leftovers from a Magic Guard user is a boon.
Oooor you could just use a different pokemon with Knock Off and be done with it.