For me, it was definitely the "challenge," but also the community. As a skiller you're part of a select group of players which gives you a strong sense of identity, you have your own hiscores (maintained by members of the skilling community), overall it's pretty tight-knit and competitive. On the challenge aspect, I've always viewed skilling (or any form of a pure) just like bodybuilding, you're constantly trying to craft your character's stats to look better and better - think of Arnold Schwarzenegger, he was constantly improving the sculpting of his body to appear better for competitions, skilling is just like that. It's just very unlike playing as a "normal" player, I really liked it for the many years I participated. For every update that occurs the skilling community is talking amongst each other, or trying to be secretive, trying to find out how to best exploit the update to their advantage. You're constantly paranoid about everything, you need to know about everything and everyone or you get left behind. Every week you get to read about the skiller that messed up, accidentally got combat, was caught botting, or just decided being a skiller wasn't for them anymore; it's like reading celebrity magazines. The player base is constantly changing, but there's always those same players present that you can count on to be there day to day, so you take comfort in that; that is, depending on your ranking - as you get higher and higher, no matter your relationship to those above you, you eventually feel the sting of envy and want for them to mess up, too. And, even though skilling has been around for a long time, there's still so many unexplored areas. Very few have actually maxed, none have yet maxed in F2P, you can choose to focus on certain skills or get get in certain minigames, or just become rich and constantly have people speculating about you. It's addicting, it's a lifestyle, and it's definitely not for everyone.