I've discussed (and then debated with folks) about this exact thing for years.
To most 'conventional rig' guitarists, their tone stops at the speaker cab. Everything else is on other folks. Sound engineers, mix engineers, etc.. You'll read posts from guys that wander out to talk to the FOH guys at shows and sit in the control room with the engineers; but the guitarist's 'job' in getting his tone stops with what ends up coming out of that speaker.
When you run FRFR systems; you are adding layers to your own 'guitar tone responsibility' all the way to the final tone delivered to FOH. With the routing possibilities now opened up *after* the actual cab/mic combination in your FRFR signal chain (ie. adding effects after the cab/mic) it can be a Pandora's box and I think from reading the many anecdotal accounts of folks frustrated with FRFR and going back to conventional power amps and speaker cabs (the so-called 'amp in the room' guys) that it can be a very difficult to understand, harness and control experience for some folks.
I think guys that come from backgrounds mixing FOH, doing recording engineering, mixing engineering and so forth in addition to being a guitarist are the most comfortable with a) the concept of FRFR; b) the creation and tweaking a full blown FRFR signal chain; and c) creating and enjoying using FRFR signal chains.
I've always characterized it as a 'guitarist's mind &)@$' or a 'paradigm shift' and this discussion is exactly what I meant by that. You are adding layers of possibility, control, concepts, complexity and options to what you can conceivably do with a guitarist's signal chain/tone and there are a good many folks that are just not going to make that leap because it isn't easy.
I call it work up front, party in the back.
Because once you NAIL what you want and enjoy it, no room, no situation, no music, nothing really changes what you 'spoon feed' FOH or a recording engineer. Everything is totally consistent and perfectly handed to the mixing board in any case; all that remains is adjusting for the room, which you've now completely simplified for the engineer by magnitudes of degree assuming you know what you were doing and did it well (creating your tones).
It's work getting it set up, and the burden of doing that is on the guitarist. Once you have 'arrived' though; it's clear sailing, zero tweaking on the gig, multitudes of possibilities on the fly with a good midi controller and some expression pedals and absolutely no pressure to cope with 'rig' variables on the gig. Your mic won't crap out, your patch cables between effects won't short; the humidity of the room won't change your speaker response.