I'd assume because of pressure from OSI and friends (i.e. bad publicity), not from the real world. The same reason my company is "open, source-available."

If the common understanding of "open source" differed so much from the OSI standard, wouldn't these companies just say "open source" and dismiss the OSI definition as archaic, too narrow, etc.? Instead, it seems like there's been a lot of work put into maintaining a formal distinction, including working with Bruce Perens to revise the BSL:

https://itsfoss.com/making-the-business-source-license-open-...

Note that I'm not coming from a position of hostility re: the BSL and similar licenses here. I think companies using that approach can be friendly neighbors with the open source community. I just think it's important for those neighbors to share a well-maintained fence to keep malicious actors from exploiting ambiguity.

No, it's not just word-play. There are real restrictions coming with source-available code if you want to use it in your business operations. One of the reasons companies express so much interest in open-source is to have no obligations before the vendor (support contracts that cannot be terminated early even if the software is being removed, licensing that makes it hard to migrate from a few large machines to many smaller containers/VMs, other forms of lock-in) and take a risk of an open-source software going unmaintained (that they usually plan to mitigate by hiring an outsourcing firm to fix the abandoned OSS projects).

Now, that is one of the main reasons why non-OSS licenses are being adopted: many companies prepare contingencies in case an OSS project dies, instead of making some arrangements to help a bit to ensure the project doesn't die. However right the vendors are, the resulting license significantly (materially, non-word-playfully) restricts the users, which is exactly why those users are compelled to start paying for the product.

P.S. None of what I wrote means I oppose those licenses, as they may be needed to ensure a healthy ecosystem. But I oppose calling them OSS.