In the music production space, you have many DAWs being given away for free, or coming with your OS, or not costing exorbitant amounts of money. My guess is nobody has been motivated enough yet to do what people like Ton Roosendaal or Linus Torvalds have done and devote years of their life to producing a viable open source alternative to the closed source (and moreover, non-free) behemoths.
I do expect that it's only a matter of time, though.
Granted, it's not perfect - some people like some of the workflows, some don't - but I find it very good, especially if you spend some time customizing keyboard shortcuts and maybe adding a script or two (it's scriptable in Lua, and you can even write audio plug-ins in that)
It supports LV2 and VST2/3 plug-ins natively, and with Yabridge you can bridge Windows VST2/3 plug-ins very seamlessly.
(Full disclosure: I have a few bugfix patches in Ardour; I'm fairly committed to it for my needs and happy to help debug crashes and such, though these days they're very rare; the developers are very responsive on IRC though!)
1) Blender is ~25 years old and has been open source for ~20. That's a lot of development hours.
2) Blender marketplace and the acceptance of the existence of paid addons by (most) of the Blender community means that addon developers can actually be paid for their work and to maintain their addons.
Addons add a lot of features that Blender doesn't have out of the box and if you're using blender professionally you are probably reliant on addons for your workflow and it is a pain when they break (which they do frequently because the API is so unstable).
Not being attacked, and even being encouraged to charge for open source software (and adddons are all open source) on the understanding that not all devs are lucky enough to work for faangs, be tenured professors or still live with our parents, and that we need to eat is something that is pretty unique in my experience.
* 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.
I’ve often heard the sound/plugin packs for DAW keep people on the paid products. Why shouldn’t there be a competitive open source option?
Edit to contextualize, and maybe an added question: Blender is amazing and competes in so many ways with high-cost, industry-standard software. How is the DAW world not a great analog and opportunity?