Well for one farmboys don't normaly wear "mail" as they don't typically fight. Hense why link starts out in the "indian/native american" gear which if you know anything about medevil villages is actually more acurate to belgum around medevil times, but anyways. He wears that because he is a farmboy not a warrior. He does not plan on going on an adventure to save the world it just happens, and his clothes change accordingly. Also, in the game you can gain magical armor which would be closer to the "plate mail" of which you speak.