Shortly before release (if I recall correctly), players were given the ability to affect gate construction, as a small nod toward player-constructed content. The system was subsequently tweaked a few times. But then missions dramatically weakened players' relationships with the Arcade. (Heck, even the Auction House did. Before that, people used to gather in the Arcade socially. Now they gather in the Town Square.) And using minerals for sprites wrecked the gate system even more.
But, as Juances' link points out, the game developers know all of this, and they are starting to think about how to revamp the gate system, to make it interesting again.
http://forums.spiralknights.com/es/node/89218