Why the fascination with subwoofers?


I have noticed many posts with questions about adding subwoofers to an audio system. Why the fascination with subwoofers? I guess I understand why any audiophile would want to hear more tight bass in their audio system, but why add a subwoofer to an existing audio system when they don’t always perform well, are costly, and are difficult to integrate with the many varied speakers offered. Additionally, why wouldn’t any audiophile first choose a speaker with a well designed bass driver designed, engineered and BUILT INTO that same cabinet? If anyone’s speakers were not giving enough tight bass, why wouldn’t that person sell those speakers and buy a pair that does have tight bass?
128x1282psyop
Dear @2psyop : Here are some reasons why I use two self powered subs wired in stereo fashion:

https://forum.audiogon.com/discussions/do-you-think-you-need-a-subwoofer/post?postid=310058#310058


You only needs two subs.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.
People that are into them are into them, and I have no issue with that, but I don't want to be bothered with all of the mess myself, and I feel my main speakers give me all of the bass that I need. 
Subs are simply just another very flexible and cost effective way to get extended bass when needed or desired , often in combo with smaller speakers with less bass extension, of which there are many very good quality affordable ones otherwise.

I use a fairly compact but extended 8" sub in one room which has tight quarters and with very high quality smaller speakers with limited bass extension that benefit.

I don’t use one, though I could, in others where the larger main speakers used do extended bass quite well alone.

I also don’t use one out on the deck where I run another pair of good quality smaller outdoor speakers with limited bass extension, mainly because I do not care about bass extension out there.

So like most things it all depends. Many ways to skin the cat, if needed.
@akg_ca 
The one big problem with all of this is that you need a good crossover to roll off the deep bass in your system and achieve all of these benefits...”
So, I gotta ask, where do I get that crossover?
Vandersteen makes their M7-HP, which looks like a high quality unit (pricy) and I would be interested but unfortunately the 100 Hz high pass is higher than the (40-50 Hz range) frequency that I would want.  Also, based on the images of their unit, this seems to be a bit more complicated than an in-line capacitor so maybe not achievable as a DIY project.

Back to the OPs question, I would look at one sub for an HT set-up and two or more for music.  By using mains with excellent sounding bass that is limited to a cut-off at about 40Hz, and then rolling in subs for their greater control at the lower frequencies below 40 Hz, I have eliminated low frequency room interactions and greatly increased bass drive.