Defining a subset of x86 that is well defined, secure, and doesn't subject your vendors to the AMD/Intel licencing duopoly, is worse than starting over with anything else.. There was even a bug quite recently about everyone misunderstanding the normal boot sequence instructions since 1980 (or so?) Then the other question is: why did you make it run so poorly on the newer mobile architectures?
It certainly seems like one could have chosen from among the existing llvm-ir RISC hardware targets and then made everyone implement an emulator.. But making a JS compatible target is accessing pre-existing emulators available on anything meant for an end user.
As a JS programmer, I don't really look forward to encountering wasm from others on sites. But I do like that I can try out any llvm language that I might be experimenting with in the web environment that I'm already familiar with.
I would never do wasm on a normal website, but it could make a lot of sense in an electron like setup. That might be a bit insane, but no more than using the Java VM was 10 years back, and without as much risk of lock in and extortion from a company like Oracle in another 10 years.
Even without other languages, it is a matter of time before my transpiler chooses wasm for me, as it is now a subset to be prioritized for optimizations across browsers..