So anyway, why should people play a healer?

To add a little more to my earlier reply:

- you like helping people, even just in overland/non-instanced stuff outside of a party you can heal and rez strangers (and even get achievements for it!)
- shortest queues other than tanks
- likely to get a comm for being halfway competent and making an effort in an instanced piece of content
- very fun challenge in PvP, especially The Feast
- self-healing in content that might be too hard to solo otherwise
- cool animations (at least in FFXIV)