It's not about losing, it's about being aggravating to play against. It prolongs matches that shouldn't be prolonged.
Like are you arguing that call in's are fine?
yes its fine. why? because there is a window of opportunity for you to exploit the lack of enemies armor with your own armor. you have plenty of time to prepare by laying mines, purchasing at guns, etc. its actually super hard for soviets to play on just t1 t2 with no fuel purchases because mg42s are ownage right now. they need some sort of fuel purchase to help break through the lines. the benefit of waiting for call ins is that individually the call in tanks are stronger than their counterparts, because guess what, they cost more. but at the same time, it doesnt make mediums invincible. also holding 2/3 of the map really doesnt fucking matter unless youre holding both fuels.