I have always simply enjoy being in support roles more than damage dealing roles. I particularly enjoy CC/debuff/buff roles in MMOs, and I'm hoping that someday that ZOS will release a class that caters to such a role.
Tanking and healing are more fun to me. Both require a lot of tactical/strategic thinking on the fly, particularly when it comes to certain mechanics that are designed to throw the group into disarray. While I occasionally like to play as DPS, I feel confined since I need to follow a certain rotation in order to maximize my DPS and therefore do my job. As a tank and/or healer, there is more freedom. For instance, as a Tank, I don't just absorb the hits. I also need to be able to position/hold that boss into the best spot for my DPS to do their thing, recognize one-shot mechanics, help CC any adds so that they can quickly be burned down all the while keeping the boss where he needs to be, and hold the line & survive when members fall and need to be revived by other group mates.
I might not be the best at following a rotation and getting great DPS numbers, but I am pretty good at trying and putting others in the best position to succeed. Which is more rewarding to me.
Oh, and the instant PUG for randoms is always a plus.