There would be very FEW reasons not to have a subwoofer:
1. You don't care about bass or the accuracy of the bass spectrum. You already like how your main speakers sound and just don't care to do anything further.
2. your room shape, main speaker location, sitting position is PERFECT and you have a linear response of sound from 20hz-100hz. This is just sheer luck of course and highly unlikely.
3. Your main speakers reproduce 20-80hz very well already. In other words they contain subwoofers. This is also unlikely.
4. Reason #2 and #3 both apply to your situation and you are already just very lucky. The audiophile gods clearly love you.
Anyone else, I would question their "audiophileness". I have had many phenomenal main speakers, even those with decent bass response, and they have always fallen short in the rooms I have used. Some songs that just happen to have notes that fall into a null on my frequency response just sounded crappy. Even great speakers would sound totally different after I moved and I could never get the same song to sound the same again. It was for me, almost always in the bass frequencies, where this was most noticeable.
Even so called "purist" claims make little sense unless you are in category 4. I would love to see the in-room frequency response of folks who claim to be "purists".
Personally I find that the listening room makes such a HUGE difference that any true audiophile who cares about this hobby enough, will ultimately have to build a purpose-built room. I'm not saying this out of simple audiophile snobbery of some sort. I suspect people are spending more money on equipment than they are on their room which is a silly way to look at things since real estate actually appreciates in value and your equipment perpetually depreciates. If you are relatively POOR... you should spend MORE on the room and less on the crap within it.
One of the reasons I mistrust audio magazine reviews: the room's characteristics are not clearly described. I have no idea if the reviewer is describing the speaker or the room. I hear all sorts of commentary about swapping this amp or that cable, but almost no commentary about using the speakers in different rooms with different absorption or diffusion characteristics. There is focus on minutiae that don't matter and little focus on gross details that do matter. Hell, most review magazines don't even describe how far they are sitting from their speakers during the listening testing...