For safely running an untrusted architecture- and operating-system-agnostic binary blob. If all operating systems could even run simple WASI cmdline blobs directly that would actually solve a real problem for me (of distributing a shader compiler executable for Linux, macOS, Windows across x86 and ARM, which is built from massively big 3rd party C++ libraries (so compiling on the user machine isn't really an option).
AFAIK Cosmopolitan is missing the sandboxing features of WASM runtimes which would allow to run untrusted code safely, and for x86 vs ARM it uses the universal binary approach (e.g. you'll either have the x86 or the ARM code as dead weight in the executable).
