Here's a bit of truth - while I have a lot of alt warriors, I don't play them much once I get them to max level. I have my main, who raids, whose gear I keep up to date and who I play often, who I indulge my transmog jones on - and everyone else, once I get them to max level and maybe get them some Timeless Isle gear, I stop. My most recent 90 warrior, a draenei woman, I kept up for a month before I finally just stopped wanting to run dungeons on her. My tauren has seen even less play.
Why? Is it just that I already have the one warrior, so why play others? No. Because even if that were the case, it doesn't explain why my shaman and my DK are both sitting there, doing nothing. My shaman makes potions and flasks for me, and that's about it. My DK is literally gathering dust. So, why then? Why am I not playing my alts? I thought about it this week while considering what to do with yet another Timeless Isle piece I could send to my tauren, and then I realized that he's off on another server, with no gold to speak of, and in order to get that piece gemmed and enchanted properly I'd have to play him for an hour or two to make the gold to do it - and it hit me. I already maintain my main's gear - doing the same work on my alts just doesn't appeal to me.
Having to get all their gear gemmed, all the enchants (I always forget boot enchants until I realize I'm slower than everyone else) - even when you can afford it (which I can for my alts on my main's server) it's just tedious, especially when you find yourself improving gear frequently. What enchants do I put on my shaman's blue weapons? Do I go for the good enchants and then replace them in two days when I get an LFR drop?
Ultimately this is what has me thinking about Warlords of Draenor. Gear has been and always will be an impediment to playing an alt - you have to be willing to put in the work to acquire new gear and get them up to the same level as your main if you intend to use them in that fashion. But the removal of the variety of enchants and gems we have now will mean there's less impediment to alt-playing.