Package managers are a lot more complex than people realize. Every attempt I've seen in every language has significant lacks for common real world cases.
Most commonly they assume all the world is their language. Very commonly they want to take over all package management but don't have a good easy story for working with the OS package manager (I know Windows doesn't really have a package manager - but you still need to interoperate with it!). Those are big issues anyone in a complex project will face in the real world, there are also lots of little warts that will bite you.
Yes package managers are nice on your trival project. However they all get in the way in your non-complex project - some more than others.