I guess we have a fundamental difference of opinion here. I play bass in bands also... so as a guitarist I try to make sure I don't trample on the bassist's freq range. As great as ...AJFA is, I hate that the bass is totally inaudible due to the guitars being so low end heavy. I happen to have a good bassist in my main band also--I want him to show through. I actually run an EQ in my line to totally cut 100Hz and below out of my signal. Sounds worse when playing alone, but in a band context it sits perfectly.
And my other guitarist has a Mesa Maverick that he loves (and sounds GREAT miced up and pulls off heavy sounds once miced up, in spite of its reputation). He's a soundman by trade and does sound at a couple of prominent Chicago clubs.
I guess I get if if you're playing a gig with no monitors and amps not being miced up. It still doesn't make sense to me when you do have those amenities. A 4x12 is not going to make a difference to your live tone--it's not like you have a room mic there to assist as pictured above. I get it in recording though only slightly, again. In fact, for live, I'd think you'd want less of that stage volume there not just due to mic bleed and less control over sound, but also for other phasing issues.
Granted, it's an extreme example, but Dinosaur Jr played at the club my other guitarist mixes at. J Mascis has 300W of cranked Marshall stacks on stage behind him, then a cranked Twin elevated and facing him from about 2:00 based on him facing noon. His vocals? Completely inaudible. His guitar tone? Shitty due to the phasing issues of the principle sound vs his vocal mic vs his guitar amp mics. Again, an extreme example, but illustrates a point.
I also kind of get if you're playing on a huge stage or outdoors. But I'm going to guess that many of us aren't playing 1000+top venues on a regular basis with a 40+x20+ stage. I generally play 300-600 top venues with decent to top notch PA's.
Again, we don't really play unmiced gigs anymore though.