I've been away from raiding for a while now (have not done anything this tier), so I'm sorry if my answer is weird in any way or does not fit the current raid content:

I raided, because concentrating on something really hard is a lot of fun
Because I can challenge myself, and because every bit of progress feels rewarding,
and it's a rush of endorphines when everything goes right for once and everyone is in sync and it results in a clear
Because I personally really enjoy having lots of mechanics to deal with, especially mechanics that can't just be ignored, and very few of the non-raid contents offer that.

I can honestly say I never once raided for the loot.
I don't like showing off, so trophy mounts/furniture/etc. are lost on me,
and the gear is a means to an end - making raiding easier, not..just "having" it.