By just sending part of the necessary binary logic to the user, it is ensured they can't easily be independent of the provider or create their own solution.
If someone doesn't see what I'm talking about, then read about the AGPL; it exists to prevent what I'm talking about.
Superficially, it is a shame Mozilla is working on this technology. However, it's official goal is to advance "The Web"©® which uses above mentioned effects to lead to centralization and lack of freedom for users.
WebAssembly and some other modern browser features are the basis for the massive centralized providers we have today. That "The Web" leads to decentralization is a lie.