Echoing your point, having a library that can do something is fantastic. Having two is even better when you have a choice on which one feels more comfortable to use and is more suited for your project. Having 25 libraries that do basically the same thing gives diminishing returns because the community is split over which one is better and easier to use, while the majority won't be full featured and with a larger number of bugs overall.

This is not necessarily a black and white scenario that holds true to everything, however. There is no such thing as an absolute generic.