You don't need to carry around a whole Javascript engine when all you want is running some WASM/WASI code. Granted, the real-world differences aren't all that big:

    - wasmer: single 45 MByte exe
    - wasmtime: single 28 MByte exe
    - node.js: 87 MByte, lots of individual files
    - deno: 186 MByte over two executables (deno and denort not sure what denort is though)

As an extreme outlier, there's wasm3 which is a WASI interpreter and which is just a single 255 KB executable (not a typo).

All sizes looked up on an ARM Mac.

Is this (size) an issue in the real world?

On desktop and server machines probably not. But more code also means a bigger attack surface.

It depends what real world is for you. In embedded or with low bandwith it might.