For one, no one needs to install WASM, nor are they going to run into versioning issues because the OS has a hard dependency on it. Every single person with a computer, from a smart phone to render farm workstations, will have WASM support because those devices will have a browser. The only browser that doesn't support it is the legacy IE line of browsers, of which only 11 is still supported, and which only runs on systems that will happily run Edge, instead.

Devs can rely on the fact that users won't need to install a single thing, and users can rely on the fact that they're not going to have to go through the insanity that is "trying to install the right version of Boobletech(tm) Meep(r)" or, hell: "trying to get their OS to even acknowledge that the preinstalled version of java is over a decade old and it needs to stop using it instead of the new version you installed".

If your compiler can target WebAssembly, and your users are on computers with operating systems that are still supported, your WASM application will work for them, because everyone has a browser.