Because it's proven to be effective. It is impossible to keep up with the speed of this game. Not just from a game perspective but also from RS gold a business perspective. Jagex at the end of the day is a business that must pay its workers, pay tax and, most importantly, make profits. If they didn't keep runescape in line with its competitors, it could quickly be a victim of.
All things are dependent on progress and adaptation Technology makes this even more essential. Although you might claim that humans cheap OSRS gold are the dominant race due to changes in their environment, it is a completely different reality.