Another one of these topics
One of my friends showed it to me a while ago, he made it sound interesting. At the time I was around 10, so it looked amazing to me - a game on the internet with skills, socializing, quests, and it's free. This was during the days of classic ... eventually I got bored around level 30, took a long break, and came back in time for the Easter event with the rubber chicken. This was probably after being really bored one day and remembering back to when I played it.
Ever since classic, I've played once a day for about a cummulative 4 years total.
I still play it because .. I want to keep raising skills with my friends on RS. Listening to RSBANDBUpdate while playing RS helps keep me up to date, so I can just log on and still have a clue about what's going on outside of the magic trees. I've been switcthing between WoW and RS a lot though ... sometimes I think I should stop skilling, and make a new character in order to try to re-live the good old days and get the excitement that I used to have. With the new tutorial, and the fact that I'm not 10 anymore, I don't think thats possible.

In the end, it's my friends on Runescape and the prospect of skilling that keeps me playing.