My question was about why one would want to call WebAssembly functions from Go or PHP.
I have a single libmysql.so file installed on my system, and it's used by Python, Ruby, C and PHP.
Why should I replace libmysql.so with libmysql.wasm?
This is simply an abstraction "everyone" has agreed on. Conceptually no different than if everyone had agreed on Java, or Python, or Brainfuck.