[matsemann]

Because so much Python code binds to C extensions that you will need to compile for the correct platform. For instance the new version of Pydantic is now backed by Rust. To avoid everyone having to compile the rust code on their platform, you can upload it pre-compiled for linux, windows etc.

[fmajid]

Some packages require build-time dependencies not everyone has, like cryptography now requiring Rust. Some packages like SciPy take a very long time to build, and require a Fortran compiler.