There are Some Thoughts on PC Rhythm Gaming on the Harmonix Blog where the company's Community Interaction Manager explains why now "really is the perfect time for the rhythm game scene to burst onto the PC in full force" (thanks Polygon). Though their similar feeling about next-gen consoles may have turned out to be overly optimistic, the company paints a rosy picture of the possibility of finding their rhythm on PCs:

(POSSIBLE) REASONS FOR THE CURRENT CLIMATE
So, why is the commercial rhythm game scene on PC so untapped, at least in the west? Save for a couple exceptions, very few big name IPs have been able to make a big splash on PC. There are a few possible reasons for this. First and foremost was the lack of awareness on the consumer side. There was no notable marketing effort for many of the PC iterations of past releases on PC. Additionally, there were typically few options that actually catered to the PC audience, including PC-focused features like graphical settings or a mouse and keyboard centric user interface.

But if there is a chance for rhythm games to break through in the PC market, the time is now.

WHY NOW?
If there’s been a perceived failure across the board with major titles, what’s going to be different now?

In my mind, the primary reason has to do with a little thing called Steam. Steam is a huge platform that has continuously grown over the years with new features to improve the community and player experience. One of these is Steam Workshop, which allows for a plethora of user generated content. Fans can reap the benefits of their dedication and talent by making and selling content for their favorite compatible games. Another important facet of this is Valve pushing for Steam to become a centerpiece of the living room experience with features like Big Picture mode.