If I needed a tank for Scholo or LBLS/UPRS, I would gladly take them (as the off tank) over waiting 2 hours to find a Warrior or Druid. That and I was a good healer that did not run with durpy DPS.
Pallies could tank better than shammies, especially in 5/10 man content, so I count them more as a tank.
You were the exception (and frankly, off-tanks in Scholo/LBRS/UBRS were a waste of a spot, bring another DPS). I was stuck healing/decursing BWL/MC all the time back then I wanted nothing better than to do something else on my off-raid times.
You can't believe the amount of crap I heard. Heck, even in TBC after Prot was fixed, you can't believe how many people would spam trade for a tank and still be there after I got out of an instance they wanted to run, as the tank, after I had offered to tank it for them.
The role also lacks the "glory factor" of other roles
Tanks do not seek glory. At the end of the day, we're happy when everyone survived and mourn the ones we couldn't protect as we would our own family. We are the shield that guards the other's in the raid.
Glory, praise, a tank craves not these things.