Levelling Alts

Having leveled my mage up to 74 already I know that I had very little rested XP last night, so I decided to level my hunter alt on Aggramar-US. I tried out some new addons to help me gather herbs to level inscription. I installed GatherMate, Routes, and GatherMate_Data. After playing around with the interface a bit on routes I was able to get a route setup for gathering herbs in the barrens, and I started running around collecting herbs. I tried enabling TomTom but it didn't seem to follow the route that I had setup so I abandoned it and just used the route on the minimap to navigate, which worked fine for me. I happened to level up (and burn all my rested xp) from clearing the mobs around the herb nodes. I managed to level my inscription from around 50 to 80, and got my herbalism to 96 after I finally realized it had been sitting at 75 for some time. I do love the GatherMate + Routes addons, and the ability to pick the specific herb types that you want to collect. It is much more productive than just running around the map and collecting the herbs that pop up on your map, although only maybe 50% of the nodes shown from GatherMate_Data actually had an herb at that location, and I came across 2 or 3 herb nodes that were not on the map.
I really want to look at the bigger picture here as well, it's clear to me that efficiency drives my efforts to level alts. I like to use rested xp as much as possible and having multiple characters that I can level at any time waiting with full rested xp bars. I originally created my alts after getting my mage to 70 during the BC era, in an effort to more fully understand the other classes to improve myself as a player. I now realize that having a level 20 or 30 alt only gives a small taste of the experience of playing a 70. Consider all the mage abilities that you don't yet have at level 30:
Mage Armor (and the improved mage armor at level 71)
Arcane Brilliance
Arcane Blast
Molten Armor
Ice Lance
Invisibility
Ritual of Refreshment
Spell Steal
Firefrost Bolt
Mirror Image
Portals
I realize there is a lot missing from my experience of other classes, and new surprises awaiting me as I continue to level my alts. So why do you level your alts? What drives you to create alts? Is it to improve your knowledge of other classes like me, or do you have other reasons?