I guess every unit in the game should use food. But if you think they don't need that, a new balance would be needed, and it would require a lot of work. There are some players that think the game needs more armies, making easier to build them, but for me it's nice.

The only problem for me it the Mech. Spam, make mech harder to build increasing oil draw.

Food is needed not to maintain the machine but to feed the people using it. Although I hate spamming large blocks of tanks and other similar to this, but tweaking it would be better.