For one this isn't OSRS, it's Final Fantasy XIV. If the developers had wanted the marketboard to be like other games then they would have made it like those games. I can almost guarantee that if they were to model the MB off of another game's then the forums would be filled with theads complaining about them ripping off those games and not having any original ideas.

As it stands the MB is the least of their concerns since it's been the way it has going on 6 years now.