Yes, true, but if you had fast units flanking both left and right on the advancing enemy army, they'd break faster and thous wouldn't cause as many casualties anyway. Since only a fraction of the unit is fighting at any moment, would you rather have the enemy killed by arrow fire enroute to your position or captured after being forced to rout? And I think the morale penalty is quite small (-2 or some such) and has hardly won the day for me in any battle.

Bridges are offcourse a totally different matter

/HG