Why aren't people Tanking or Healing in WoW?

Spec Breakdown for the 10 Classes

DK - 2 Dps, 1 Tank
Druid - 1 Dps, 1 Tank, 1 Healer
Hunter - 3 Dps
Mage - 3 Dps
Paladin - 1 Dps, 1 Tank, 1 Healer
Priest - 1 Dps, 2 Healer
Rogue - 3 Dps
Shaman - 2 Dps, 1 Healer
Warlock - 3 Dps
Warrior - 2 Dps, 1 Tank

21 Dps, 5 Healer and 4 Tank Specs. The amount of Dps to Tank/Healer specs is really crazy. 21 out of 30 specs are for DPS. That is 70%.

In previous games there has always been a difference in the amount of dps to healer and tank classes. In the original EverQuest the class breakdown was as follows:

Tanks - 3 (Warrior, Paladin, Shadow Knight)
Healers - 3 (Cleric, Shaman, Druid)
Dps/Support - 8 (Monk, Ranger, Rogue, Wizard, Magician, Necromancer, Enchanter and Bard)

8 out of 14 classes are for DPS. That is 57% roughly.

For EverQuest it was necessary to have a group to play and get experience/level. In World of Warcraft it is necessary to level by yourself and to do so you must choose a DPS spec.

There are two colliding Worlds in the World of Warcraft. The world of questing by yourself and the world of running a dungeon. The two don't fit together very well at the moment. It requires messy things like.. Dual Specs and what not. It forces the player to learn to play one spec while questing and another while in a dungeon.

The issue is when I log in as a level 1 and want to be a healer I can't really do it until I hit level 15. From then on I would have to use the dungeon finder for the rest of the game.

The solution? The best idea I can come up with is a way for people to queue up for questing rather than a dungeon. Lets call it the 'Adventure Finder'. You and 4 other adventurers would be placed together to do quests in the game. It could be cross server or restricted your own server. It would encourage teamwork and would reward bonus experience for being in a group.