It helps a bit if you specify when, date-wise, you last played. The release of "skill capes", which are cosmetic capes (with decent defence bonuses) that can be obtained after you get 99 in a skill, motivated a lot of people grind just to get 99s in a skill. Some of it may also be due to the more higher-level-oriented content that Jagex has released (ancient effigies...and stuff). This is all assuming you left before skill capes.