1. to create web versions of applications that are traditionally desktop only to render things like Parquet, PSD, TIFF, SQLite, EPS, ZIP, TGZ, and many more, where C libraries are often the reference implementations. There are almost a hundred supported file formats, most of which are supported through WASM

2. to create plugins that extend the backend and add your own endpoint or middleware as a way to enforce the code run in a constrained environment without the ability to send people's file out

3. in the workflow engine to enable people to run their own sandboxed scripts without giving those a blank check to go crazy

But also - it's lacking things like a unified positioning + required knowledge to understand it is quite large compared to average dev + most people have no real use for it. It's mostly too "abstract high level" and "low level" for most devs.