After playing my pure mage character for a while, I finally got Expert Robes. So then I was going to buy an Expert Hood to complement my robes; but I couldn't find it in the sellers inventory. At first I thought I just wasn't a high enough lvl. Then I searched in uesp.net and find out that there are no Expert and no Master hoods in Skyrim. My question is why is that? Tight development time? Laziness?

Once you're an Expert, you're too cool for hoods. Everyone should see your glorious face and envy your power!

That could be the reason. All jokes aside though, you would think that bethesda would know to add in higher lvl hoods. Novice-Adept get hoods, so why leave out Expert and Master? It makes no sense.

On my non-enchanting character, I wear a dragon priest mask or a circlet. 100% Magicka Regen with Morokei, or 20% Fortify Destruction with an Eminent Circlet.

If you are an enchanting character, You can enchant your own hood. Colette Marence (Restoration) sells unenchanted mage hoods. You can get +73 Magicka and 29% Fortify dual enchant. Or 2 schools. Better than anything you can receive, earn, find or buy. I also like the looks of Alik'r hoods for mages. You can buy them at Radiant Raiments in solitude.