I guess thats cool that they have a plus 3 morale , but..
usually i'd only built peasants when i just need 1 or 2 units to bolster the garrison ,,usually i'd never want more than 2 units of peasants in any army - and i try not to use them at all..
but they are useful for certain things - dieing mainly lol (to take archer fire , instead of my more expensive troops) or.. to be in the back of the line to increase numbers..
putting them in the front line tho is not good, because they'll rout and possibly cause a mass-routing.. you know how it works, 1, then 2, then 3, and then ur entire army is broken..

but Highlanders tho,, sheild and axe are a beautiful troop