The VOIDRUNNER'S CODEX is coming! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
It isn't just tanks, it is Imperial hardware, in general. The Empire likes such things because they strike fear into people. And the Empire generally feels that men and materiel are expendable. They don't really care so much if they lose a few tanks because they are easier to hit.
The Rebels, on the other hand, are not interested in quelling populations, find individuals hard to replace, and are strapped for resources. So they tend to favor small, agile systems.