Only a handful of companies make open weight models, and those models are not made for charity. They want either market share and/or control. Making your own model is not like making your own software because the capital cost are extraordinarily high. The masses will not have the billions in funds they would need need to train these models
Unlike open source code, you cannot check what's actually in the open weight models. Worse still, you can hide things that trigger on very specific words (poison attacks can be intentional by the model maker or put by other actors in the public data). Fine tuning attempts are also no escape from hidden features you don't even know to look for