As a healer myself (with two level 60 priests at my disposal), I find this post discussing why so few people have a desire to play healers
to be rather interesting. The favored theory, by both the original poster and subsequent responses, is that staring at health bars isn't very exciting and playing whack-a-mole with the health of your party members just isn't very much fun. In my case, I find the importance of the healer role to be the exciting part - your action (or inaction) has a very real impact on whether your party lives or dies. However, perhaps I haven't played the class to the point of burnout yet, which seems to happen to many healers at some point or another.