by sigmazero13
I think that would make routs more powerful than they need to be. If the other army is completely routed already, chances are you've won the battle (although it's not guaranteed, if they have a stronghold and the attacker lost strength).Routs wasn't intended to cause actual damage, it basically represents them being scattered and disorganized - still there, but not "dead". Scattering them again doesn't really do much.
However, this is a pretty rare situation, from my experience.