Mistwell
Crusty Old Meatwad (he/him)
Wizards are not typically walking around with a 20 Dex. First priority for a Wizard is Int, because spellcasting is their thing. Second priority is their concentration checks, because concentration spells are their best spells. Which means a feat (War Caster, Lucky, whatever) and/or boost to Con (and you cannot dump Con). Which means your THIRD priority is Dex. You're not maxing your third priority at anything aside from very high levels, if you're using standard array or point buy.
If I had to venture a guess, I'd guess a majority of Wizards have a 14 dex for most of their wizarding adventure days. Which means AC 15. Which is NOT PLATE ARMOR. And if you instead increased that Dex, it was at the expense of intelligence and constitution (and a feat to help concentration saves) which means you've just made yourself highly vulnerable in another area (hit points, concentration saves, potency of spell attack bonuses, damage bonuses, and save DCs, etc.) to make yourself less vulnerable to this area of AC. Which seems a really bad strategy for a spell which is easily dispelled and which only lasts 1/3 the day.
If I had to venture a guess, I'd guess a majority of Wizards have a 14 dex for most of their wizarding adventure days. Which means AC 15. Which is NOT PLATE ARMOR. And if you instead increased that Dex, it was at the expense of intelligence and constitution (and a feat to help concentration saves) which means you've just made yourself highly vulnerable in another area (hit points, concentration saves, potency of spell attack bonuses, damage bonuses, and save DCs, etc.) to make yourself less vulnerable to this area of AC. Which seems a really bad strategy for a spell which is easily dispelled and which only lasts 1/3 the day.