Now, with systems like npm, maven or cargo, all you need to do to get a package is to add a line in a configuration file, and it fetches all the dependencies you need automatically from a central repository. Very convenient, however, you can quickly find yourself with 100+ packages from who knows where and 100s of MB of code.
In C, traditionally, every library you include requires some consideration. There is no auto-download, and the library the user has may be a different version from the one you worked with, and you have to accommodate it, and so does the library publisher. Or you may have to ship is with your own code. Anyways, it is so messy that the simplest solution is often not to use a library at all and write the thing yourself, or even better, realize that you don't need the feature you would have used that library for.
Bad reason, and reinventing the wheel comes with its own set of problems, but at least, the resulting code is of a manageable size.