People like the customization because it's fun. At the end of the day it's a game meant to provide entertainment and I for sure am one of the people that gets entertainment out of customization.
I get why customization, but I thought, that customization is for having light tank battalions for encirclements, cheap tank battalions as reserves against landing, heavy tank battalions against heavy entrenchments, infantry tank batallions as support for infantry, tank destroyer battalions against enemy encirclements, etc. But I saw lot of "I want light, medium and flame tanks, all inside one battalion". And I don't get that.