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?
2psyop
steakster
I moved my Talon Roc out to sell and have more room. But it turns out I have plenty of room. Soon as I can find the time its going back in. Mine's powered so I will be able to set it to do very little but add a little at the extreme low end. If it even will do that. Was never able to get it to go as low as my bass array does already, but then with one you are forced to locate it for least bad overall. So we will see.
   clio09,
      I can only tell you what my definition of 'tight' bass is, which I realize may be a term that has different subjective meanings to others. A bit difficult to describe but easy to identify when you hear it.  
     Tight bass to me means accurate, solid and natural bass. The leading edges, the pitch and tone, the duration of the sound, the volume, the impact and the decay of the bass all are perceived as accurate and natural.  There's also no sense of exaggeration, attenuation, blurring or something added to or missing from the bass.  In other words, the sound of bass instruments sound right and tight, just as they sound when played well and heard live in person.
     I've also personally noticed that, if the musicians get too drunk, then you often don't get that proper degree of funk.

Tim
Thanks for all the links, it has given me a better understanding of subs and setup. 
Can someone define for me what "tight" bass is.
An artifact of sound reproduction. It does not seem to occur in real life. Punch but no detail, in a nutshell.

To address Raul's attacks against me: I don't sell speakers of any sort. I recently moved, and now have a standing wave in my new listening room. I've seen how effective the Swarm addresses this so I know they will work in my situation. I only need two, as my speakers go down to 20Hz no worries.