Drivers aren't much of a threat to the Windows hegemony because since Vista they've needed to be signed. If you don't mind taking the risk of running with driver signature verification turned off you can get FSDs for XFS and Ext4.
However, being able to support the driver so it passes the certification process with every update is not something many tech enthusiasts would want to do.
Certification is only required if you want to display a "Certified for Windows" logo, prevent a warning dialog from displaying on Windows XP, and/or distribute your driver through Windows Update.
