A real bowed string instrument can offer a wide variety of sounds. Combine that with the difference in sound based on the number of players, recording space, and mic'ing techniques, and it's unreasonable to expect one library to cover the full range of sonic possibilities.what's the point of doing so many strings library? does it mean that this one is not good enough? (no offense intended)
Sometimes, these options are crucial to a project. Sometimes, hearing something new can break you out of the creative doldrums.
Yes, it can get a bit silly. Does anyone really need CSS, Vista, and Con Moto? Probably not.
Unfortunately, an alternate library can also be nice to have around because of goofs in another. Maybe a bad take or sloppy transition can stick out too much if exposed, so you might need to sub something else in. It sucks, but it happens.