Because since Runescape was bought by the new investors it's primary concern is micro-transactions and other such scams.
They're also trying to compete with other, modern MMO's like LoL, WoW and Diablo - when we all know a game like Runescape in terms of graphics and content just can't.
Runescape's USP was it's simplicity and competitiveness to be up in the high scores. Today in EoC, everyone and anyone has a maxed account with 60000B because the game is just stupidly crammed with buyable armour and crappy looking pets. They're trying to make Runescape something it isn't, which is why it's lost it's simplicity. Also, there are so many EXP boosting items and methods, that 99's now take no effort to achieve.
I wouldn't be one bit surprised if Oldschool Runescape outlasted EoC.