
I think people sometimes get pigeon-holed as healers. They just get used to you, the player, being a healer, and assume you won't mind taking that role.
I took this, and a lot of other commenters in mind, when I tried to join groups and look for PUGs the past few weeks since writing the article, to see what happened. I monitored others' reactions and requests, as well as my own, to gauge the situation. A lot happened over that time period to give me plenty to think about.
Certain situations spring to my mind rather quickly. I was whispered to join a ToC 10, and was asked "which of your healers do you want to bring?" It wasn't "which of your characters" it was healers. This person was aware I had a hunter, but that wasn't what they wanted. When I joined the group on Bellbell (because Bellwether needs nothing that doesn't drop off of a Hardmode ToC 25), it was empty of anyone but him, me, and another healer, so it wasn't just a case of needing a healer.
Another raid was an Onyxia 25 in which I had finally been invited as Retribution DPS. Some guild members were tanking and DPSing, but it was mostly PUG. And then it is revealed...we have only four healers. All PUGs.
I should have kept my mouth shut. I shouldn't have asked "just four healers?" I should have just kept going as DPS. But I didn't. I said "just four healers?" and immediately my guildmates frantically requested in guild chat, in the spirit of not wiping, for me to switch. Of course, I caved in with much grumbling and sourness of mood. And we downed her first try, I "won" healing meters by a wide margin, and I died inside a bit.
Following that we went to ToC 25, and I was invited along as a hunter. With no pressure on me, with no one requesting it, I ended up switching to Bellwether to heal the instance because we couldn't find other healers. We just couldn't keep more than four online, and I switched. And again, I did 10-15% more healing than any other healer there. The one following most closely was a guild member's alt who had just hit 80 with an ilevel 175 blue mace.

I did note with pride that I was in the top three of Damage Done and DPS. Even though there was no Ret Paladin in group, so the raid received my Ferocious Inspiration buff, I felt singular and replaceable.
Then, in a VoA 25, we downed both Koralon and Archavon. Yet, we wiped twice on Emalon before I left. Switching was slow to the Overcharged, and with several people (Warlocks, even!) doing 1k DPS, they weren't killed fast enough. And though I hit every cooldown I could and topped both Damage Done and DPS charts, I couldn't cover for those slacking people. When someone has low HPS or Healing Done, I can cover for them. I can pick up the slack and throw out heals left and right. But I can't push someone else's DPS, even when I'm hitting 5k+ myself.
So, what is really locking me into the healing role?

But, there is definitely blame lying squarely on my shoulders. That ToC 25 I was in on my hunter? No one asked me to switch. They told me I didn't have to. But I did anyway, even though my Hunter is the one who really needs the badges and Trophies, so my boyfriend's Shadow Priest could come in the raid and so we didn't have to wait for healers through the disconnects and random leaving due to impatience.
I still heal because I enjoy it, certainly. It is fun and dynamic and involved. But I also heal because it's what's expected of me. I heal because it often gives me more control over the outcome of the raid. I heal because it takes less time than trying to PUG a healer. I heal because I don't trust PUG healers. I heal because it makes me feel useful. I heal because I want others' runs to go smoothly.
While it might be easy to blame others for pushing me into this position, it wouldn't be fair to deny the role I've played in locking myself into healing.