Why do so many programming languages have their own package manager?

cross-posted from: https://sh.itjust.works/post/64685863

Lots of programming languages have their own package manager, separate from the distribution or OS package manager.

Going loosely from the TIOBE index:

• Python has Pip
• C# has NuGet
• Javascript has npm for Node.js
• Visual Basic also uses NuGet
• R has a repository of packages that can be installed by running install.packages("something") in R
• Rust has Cargo/Crates
• Go has the go get command
• Swift has its own package manager swift package
• Ruby has RubyGems
• Java has Maven and Gradle (not sure if they are full package managers, or build automation tools with dependency resolution)
• PHP has Composer for managing libraries and dependencies
• C and C++ are the only exceptions I can think of, off the top of my head; libraries are managed by, and coupled to, the operating system