there are only rmt spammers because there is a demand, which comes from the players.
Right, but when honest players like me can't perform simple actions to block out that spam without completely turning off /tells or /shouts, then that's a problem with the game.

These are two separate issues. There's the problem (in all of gaming) with gamers trying to get ahead by buying currency, and then there's the problem of game developers building their clients to minimize these impacts.

There's really nothing SE can do to solve the societal issue, but there's plenty SE could do to fix its game.