Ask HN: Why doesn't more failed startups Open Source their product?

What's stopping them? Code quality? Copyright? Or maybe they just don't care? I've seen a lot of annoyed customers in the threads lately complaining about not going to trust small startups again. And I don't blame them. I'm pretty certain products like Sparrow, Grove.io and more could really flourish as Open Source projects, but instead they're left to die... Would really like to hear from someone with a previously failed startup.