Could be a lot of reasons:
* There it's a strong "vendor lock" in DAWs (Studios don't like to invest in re-training their audio engineers)
* Lack of a strong initial sponsor that creates momentum.
* Codecs with patents that can be scary
* I don't want to imagine what a mess should be with the QA of the VTS plugins out there or things like ASIO drivers for interfaces.
Blender is a rare case: Exists in part thanks to a lot of studios taking the risk of using it, therefore a few professionals want to use it, which made more studios want to use it too and sponsor it, which attracted more users, creating momentum, then a positive feedback loop.
In any case, right now I'm happy with Reaper. It's cheap, reliable and easy to use. For people hardcore into the free software movement, are usually fine with audacity (at least the forks without spyware). I bet all that make the incentive to make a new FOSS DAW reduce even more.