Tiny F2P bank spaces is one of the many ways Jagex pisses you off to the extremes until you finally fold and become a member. But hey, they get money, you get good stuff. Everyone who counts is happy. Actually, a common thing in most games with a P2P option is that they give the free players the smallest range of capabilities they can possibly do and still have the free version of the game be decent, and give paying players all the good stuff, and the decent stuff free players should have anyway. Over time, some even make once-F2P capabilities P2P-only (such as IMVU beginning to charge for viewing licenses or whatever they're called - if you don't know what IMVU is, don't bother asking).