Because you want to program in Rust but have a specific need no Rust library full fills but Python libraries do. Suppose you need to convert between Gregorian,

Because you want to program in Rust but have a specific need no Rust library full fills but Python libraries do. Suppose you need to convert between Gregorian, Julian, Islamic, Hebrew, and Armenian calendar dates. No such library exist for Rust but they do for Python. So you either spend (waste) time writing one for Rust or you use this Python binding.