Above all Graal is a company, and if they want to keep the game running they need to make money. Sparring/PKing/Towering brings no revenue to them whatsoever. However, revamping Castle with a bunch of new goodies, making new hats/GFX, opening new shops, making Nexuses and Revolutions, and overall making new stuff that can be sold does bring the game money. They have their priorities.