I just don't think the language will thrive as well as it could if the number of users is limited by a financial barrier. Sure, it will have users, and sure, they will find it useful, but a lot of its potential will go unrealized.
You could make the same argument with tools, so why are languages different? I think because they are more foundational.. other tools are built IN them not just using them. They become a substrate. Or not, if they're not widely used.