man bucklers were not just a "civilian" shield, they were the shield that was actually in use in battles, melee infantry was not carrying big shields into battle past the roman era(asides from specific pavise spearman or xbowman, there were even more actual skilled melee units that were sword and buckler men)
I mean sadly a buckler breaks in a second in the game, with the new difficulty they should be in 200 hp range, I mean even though its small its all metal, they were effective at blocking big weapons and being able to get in for a kill(like killing pikemen, etc IRL)