My guess is that all these major tech companies are seeing Microsoft, Google, and Facebook gain a lot of recruiting clout and general industry goodwill through their other successful open-source projects.
So now there is legitimate incentive to develop and get adoption for your own "faster Python" project, which (if successful) could end up being used by millions of developers around the world. Imagine the clout and name recognition that would come with being the company that finally made Python fast after 20+ years of failed attempts. Not to mention all the free labor (bug reports and PRs) from the open-source community, all while optimizing the tool to serve their own internal technical needs above all else.
That's my only explanation for why these companies are all DIYing their own project and not contributing to existing efforts like PyPy and HPy. I think ultimately this work is all good for the Python ecosystem, but clearly I'm a bit cynical and skeptical of large tech companies' motivations in general.
Maintaining internal forks is time consuming and expensive. For big tech companies they might end up saving money on infrastructure but small companies can end up sinking a lot of human resources into the project (especially if you're playing whack-a-mole with upstream changes moving in different directions and breaking things)
Open sourcing things increases the likelihood it'll be upsteamed (the use case is more obvious) and increases the likelihood you'll get support (although you now have a community to support). In addition, it's easier to plead your case if upstream breaks something (here's my source vs vague statements about an internal thing at company x)
So now there is legitimate incentive to develop and get adoption for your own "faster Python" project, which (if successful) could end up being used by millions of developers around the world. Imagine the clout and name recognition that would come with being the company that finally made Python fast after 20+ years of failed attempts. Not to mention all the free labor (bug reports and PRs) from the open-source community, all while optimizing the tool to serve their own internal technical needs above all else.
That's my only explanation for why these companies are all DIYing their own project and not contributing to existing efforts like PyPy and HPy. I think ultimately this work is all good for the Python ecosystem, but clearly I'm a bit cynical and skeptical of large tech companies' motivations in general.