Sorry, who's the "everybody" who wants to mandate open weights? The only discussion I'm familiar with is that some people and governments want to ban open weights. Where are you seeing people argue for mandating them?
It is not something you hear from the people in power - so it has close to zero chance of becoming policy - but you can see it mulled on places like HN.
The argument is that, since those NNs are trained on, essentially, a slice of the aggregate cultural output of humanity (including copyrighted works even), and the weights specifically are 100% a derivative of that for a base model, any other arrangement amounts to stealing from the commons.
