You can demand it but it’s not an pragmatic demand as you claim. Open weight models aren’t equivalent to free software, they are much closer proprietary gratis software. Usually you don’t even get access to the training software and the training data and even if you did it would take millions of capital to reproduce them.

This is a problem that can be solved by creating open source community tools. The really difficult and expensive part is doing the initial training.

You can put into your license whatever you want but for it to be enforceable it needs to grant licensee additional rights they don’t already have without the license. The theory under which tech companies appear to be operating is that they don’t in fact need your permission to include your code into their datasets.

There have been numerous copyleft cases where companies were forced to release the source. There's already existing legal precedent here.