Just because you say so?
For example, how can you say the Kubel under performs when the wc51 for 10 manpower less can transport units, cap, upgrade to have a gun that has more dps and range (and can suppress can it not?), has more Armour, has mark target and can call in artillery?
probably cuz
1) it is doctrinal,
2) it doesnt spawn with any GUN and
3) Kubel gets free maphack at vet 1