VC=Guerrillas, no tanks, no artillery, no jets, no SAMs. Which is why they were guerrillas, thats all they could do.NVA=Regulars, had tanks, artillery, etc. Could and did fight conventional warfare...
There are many reasons like to destroy the forests so troops could locate the Viet Cong. To create military bases on which to station forces and supplies, also for the snipers that hide in the trees