Thing is, about Shield, is if you get attacked twice a day, you're better off with Mage Armor...and Shield stacks with Mage Armor. If you honestly think you need Shield, then you may as well have a better Shield while you're at it.
So Shield only makes sense if you figure you'll be attacked...
Ooh, that's a good point, a mage that's already wearing armor sure won't need it. Anything else?
"Don't wanna", on the other hand, isn't quite what I'm looking for. 5e is pretty robust (with a sane DM) so a player rolling up a wizard with an 8 Intelligence isn't going to "wreck" the game, but...
Sorry if this is a double post. My question is: is there a decent argument for a wizard (specifically) not casting/using Mage Armor past level 3 or so?