I have used a sub for years with my bookshelf speakers. Recently, when I switched to floorstanding speakers, I tried setting them up without the sub. I was never able to achieve the quality of bass in my listening room that the sub provided. So I added the sub back to the system.
My use of a sub is not because I like things that go "boom." In fact, the hallmark of a well integrated subwoofer, IMO, is that you cannot hear it until it is turned off. That level of integration is difficult to achieve. In my case, it required a long effort with digital room correction, EQ software, and a good microphone. But the results were worth the effort.
One benefit of using a sub that I don't think has been mentioned so far is that it can significantly improve the perceived macrodynamics (i.e. headroom) of your main speakers. I have found this to be true with both bookshelf and floorstanding speakers.