Look, everyone has their own style of wearfare. Some people show up in full battle rattle with mirror finished armor. Others show up to look good.

I read somewhere that the armor distributes blaster bolt shock through it so all the Stormtroopers get knocked unconscious. They don’t die, otherwise they may as well not wear it at all as they fall over after one blaster bolt.

But as with everything in Star Wars lore, that’s probably a desperate retcon.