I just found out there is no penalty for wearing armor? Why would anyone wear robes then? Provided you can enchant armor?

roleplaying, alteration spells, more diversity in character appearance, magicka regen/cost reduction if you don't plan on enchanting...

Because you don't want to invest perk points into an armor skill? Because robes weigh less, don't slow you down, and allow you to carry more loot? Because there are perks that increase your magical armor rating when wearing no armor, thus making shield spells better? Because your character vision is of a mage who doesn't wear armor? Because you can get better magical enchantments on robes and hoods in the early game than you can by enchanting armor?

Well, the ward spells are more effective if you're not wearing armor... and those spells can absorb magicka (with the perk)

But if you want to play battlemage, that's fine, really.

Roleplaying..? Simply wanting to..wear robes? Personal preference?

I don't see how you don't see the many viable options as to why someone would wear robes. Plus there is a perk that benefits wearing only robes/hoods.

Personal preference?

I used robes and cloth early on because they all came with free enchants.

When I got stronger, I picked what I thought fit the look of my character and enchanted it thusly.

As Pen said though, Alteration perk would really be the only rewarding reason outside of roleplay if better options are available.

*EDIT*

Get out of my head FTW! >_<

I don't play as a mage and I still were robes and clothing. It allows you to spend more perks on other skills instead of dumping them into light or heavy armor.

This reminded me

http://www.youtube.com/watch?v=vqO7zEWu0W0