Because he doesn't, I bought him some and gave them to him but doesn't equip them. There is a chance they were the same as whatever he wears by default. I have given him ring and a circlet which he put on fine.

Has anyone got Marcurio to equip a robe other than his default one? And does anyone know what enchantments his default robes have?

Thanks

He does... eventually. I gave him the dark brotherhood robes and he only equipped when we zoned out of a city

You wouldn't happen to know where I can get some Robes of destruction for him do you do you?

Not sure but this would be you're best bet

http://elderscrolls.wikia.com/wiki/Radiant_Raiment

Faraenger at Whiterun sells robes, also might get some at Winterhold college.

Mine doesn't, he seems to prioritize armor over item enhancements - so he will wear heavy armor over anything with +magica/+destruction on it, except for the chest where he will use light armor (not robes).

I did try with the two lower tier destruction robes (not sure how many there are) and he won't use them.

He won't use staves either, he is typically using the best two-handed melee weapon in his inventory only to use magic in both hands when actually in combat.