On one hand it absolutely does allow for niches to be filled, but on another it's a dumpster full of trash with gold in-between. There's a danger of either fatigue or slump sales over time. Maybe another Nintendo Seal of Quality on the horizon will emerge.
While Steam could do that, there's no incentive for them to. They can lay out $0 into such a project and let third parties sift the trash for them and do journalism on letting potential customers know what games are good. Win-win.
