We learn a lot form playing on our own, but by doing only that we can miss some of the nuances of our class. We can also read up on classes on websites like this one or specialty forums. Some people would like to be taught in a more direct manner. At some points, we've all taken others under our wings to show them the ropes. Most of us have gotten a few pointers along the way. We have mentors in most of our roles in life, so doesn't it make sense to have them in WoW as well?
It can be hard to directly ask for assistance, especially in a places as prone to ridicule as the WoW General Forums. Apollymi of Greymane is looking for someone to teach her to be a better rogue. She said she's read the right guides but hasn't gotten the necessary experience to match other Rogues. She's looking for someone to mentor her in all things Roguish.