Maybe you don't, but others do. To be able to achieve 99 in all skills non-combat without using combat as a way of getting money makes it more challenging. It's less likely for a skiller to buy 99 cooking, firemaking, herblore, fletching, crafting, & smithing. Plus, it's not necessarily limiting your gameplay. You can train combat at a later date if you want. Anyway, I've figured out what to do - stay a skiller until I have quite a few 99's.