Ports arn't a bad thing, bad ports are a bad thing. PC has good ports, because ports mean more money.
Also, just because it isn't the largest share doesn't mean that it's not still profitable. Just because potatoes outsell Yams doesn't mean that were going to stop selling Yams.
Lastly, PC supports consoles. Where did User Generated content come from? PC. DLC and most Indie game developers? PC. Mods? PC. Digital Distribution? PC. Steamworks for the PS3? PC. Online gaming and gaming services? PC. Split Screen and Coop likely started as LANing. Most Genres have there roots in the PC. And PC offers the most choices, the most flexibility, most openness, and the most power to make new visions come to life. Now, I'm trying not to be a PC elitist here: We have to deal with more piracy and more DRM, less certainty that our hardware will work for a specific game, less brand recognition, making developers not pay as close attention, and more expensive hardware. But we also have mouse and keybioard, cheaper games, free, automatic internet, a platform with more uses then a console, and upgradeability. PC is just the most DIFFERENT platform. And because of that, it acts as a great place to experiment with the genre. It may not be as popular, but it is still essential for the success of video games.