It's cause the KV8 is the soviets hardest counter to infantry, where it forces the German player to absolutely tech to armor or get demolished.
Not really. The KV-8 needs 4CP, the timing of which suprisingly falls together with the first PzIV. That's assuming the Soviet didn't tech and is still on tent. Since there is absolutely no reason not to spam PzIV as Ostheer, the best the KV-8 can attempt to do is a baserape.