Because its killing the game. The only real doctrines that matter have all call in tanks. otherwise you putting yourself at a rather major disadvantage as your opponent can simply forgo tech and have far more fuel available for his tanks then you have for your non call in tanks.
This especially true for the kv1 t-34/85 and sherman which can easily replace the entire tier 3.
So any doctrine that doesnt have call in tanks are put at disadvantage and i really want to level the playing field between doctrines. this makes the game more fun as other doctrines and strategy's become available.
It's also completely killing the option to build howitzers outside of the Soviet counter attack doctrine and the German Joint operations doctrine. You just need to pour too much resources into countering the heavy tanks to ever be able to get a howitzer out.