I hope you meant underperform....
Yes, you're right, I wrote it wrong.
Edited.
I think the main reason it was mandatory to have tanks in vcoh is at guns. They were as cheap as an inf squad, they built quick and had punch. The dynamic of costly, slow to build at guns in coh2 makes fielding them , especially in an emergency quite difficult. The patch helped by making them a little cheaper but 320 imo is still too much.
I don't know why they were made harder to field, but it's obvious the outcome is at guns not actually being a hard counter to tanks. Which means it's almost mandatory that you have tanks to fight tanks in coh2.
To add up that they are expensive, they are also slow and vulnerable to everything that isn't a armor vehicle coming straight ahead. Sending an ATgun to the frontline can take several minutes, just to be intercepted midway by a enemy unit, killed and stolen.
Is much more safe to invest resources in tanks to counter enemy armor because they are not as vulnerable, also they're more useful and only slighty more expensive in terms of mp, and to sum up, in the soviet case it only can be produced in the T2 building which for some players is not viable in their build.
It's not strange then than mid and lategame is a constant spam of armor vehicles for both sides, setting aside infantry only for capping duties (not even necessary for soviets).