It is, that’s what Windows does. It’s also possible to compile programs to not need external libraries and instead embed all they need. But both of these are bad ideas.

Imagine you install dolphin (the KDE file manager) It will need lots of KDE libraries, then you install Okular (KDE PDF reader) it will require lots of the same library. Extend that to the hundreds of programs that are installed on your computer and you’ll easily doubled the space used with no particular benefit since the package manager already takes care of updating the programs and libraries together. Not just that, but if every program came with it’s own libraries, if a bug/security flaw was found in one of the libraries each program would need to upgrade, and if one didn’t you might be susceptible to bugs/attacks through that program.