[callahad]

Mainly because things might work differently in a WASM runtime than they would in native code. A chief example is filesystem access. The WebAssembly System Interface (https://wasi.dev) uses capability-based access to files, so WASM modules are unable to open or write to paths that are not explicitly passed to them, with appropriate permissions, by the WASM runtime.

So there's effectively another layer of sandboxing versus a native binary, and you might need to track down how your program behaves in that sandbox.

Similarly, if you're working with a program that imports several WebAssembly modules, you'll need a way to debug the combined system, versus any single module in isolation.