The OP asked, and I think it is safe to assume that book shelf speakers are usually used where lack of space or desire for a smaller less obtrusive speaker is needed. For the most part, they are a compromise which usually lacks the ability to reproduce the lower frequencies. In the past sub woofers were not that common but when Home Theater systems became popular subs become more common which helped to close the gap between smaller speakers on stands and floor standers capabilities to offer a full range.
When it comes to a small space book shelf speakers will often be enough to keep most people happy as the volume of the room is small enough that a book shelf speaker will offer plenty of db's of SPL. A larger listening space a book shelf speaker might not offer what you want as you might need or want a speaker that can push more air.
While I see many post claiming that best is what you decide, well I say what you like best, might not really be best, perhaps it is enough to keep you happy, but their are less capable, and more capable, or ok, and better.
Some people have less requirements than others.