That is not what it's being asked.
As a developer, you just need to provide the code and the list of requirements. And maybe some guide about how to build and run tests. You do not want to care about where I find those dependencies (Maybe I'm running you code as PID 1).
But a lot of developers want to be maintainers as well and they want to enforce what can be installed on the user's system. (And no I don't want docker and multiple versions of nginx)