We have epic followers, we have a legendary follower, so why not heirloom followers?
Well, as is often the case when I have one of these ideas at three am, there are potentially a lot of reasons why to not have heirloom followers. For one thing, we level our followers and get them better gear and so on - a follower you could somehow send to your alts would mess up this whole process. Would they scale to your level? What level would they top out at? Could you gear them up? Could you make them epic?
All good questions. But man, it's daunting to have to try and get all the same followers over and over again, especially ones that are on rare vendors. Sometimes I wish I could mail my little minions to my alts, just so I wouldn't have to deal with flying out to the Spires of Arak yet again.