Because those other ecosystems assume that someone has already done the work on the base system and libraries that they don't have to worry about them, and can focus purely on their own little islands.
More like, in other ecosystems, especially the compiled languages that weren't born as part of UNIX like C and C++, the whole infrastructure also takes building and linking as part of the whole language.
Note that ISO C and ISO C++ ignore the existence of compilers, linkers and build tools, as per legalese there is some magic way how the code gets turned into machine code, the standards don't even consider the existence of filesystems on header files and translation units locations, they are talked about in the abstract, and can in all standard compliant way be stored in a SQL database.
Note that ISO C and ISO C++ ignore the existence of compilers, linkers and build tools, as per legalese there is some magic way how the code gets turned into machine code, the standards don't even consider the existence of filesystems on header files and translation units locations, they are talked about in the abstract, and can in all standard compliant way be stored in a SQL database.