There's also a lot of sticky points at the bottom of the stack that lead towards native solutions, starting with memory management and basic I/O functionality.

There's also a lot of sticky points at the bottom of the stack that lead towards native solutions, starting with memory management and basic I/O functionality. Nobody wants to code directly against the hardware for very long, so you end up with a driver, and then driver and resource management, and then an operating system of some kind. Even on the early microcomputers it was the case that you have a boot ROM of some sort and would code against that for most tasks. With WASM you have the same kind of thing but the added wrinkle of the browser-based I/O being a different set of "basic abstractions" from what you get in libc, and every solution that bridges the gap being a bit of a hack. Being bytecode doesn't really change the fact that you still have to deal with the resulting dependencies at some level.