Help me understand the role of amp modelers
I've been a long time bedroom guitarist and have recently joined my first band. We've rehearsed together a few times and are gearing up to play live shows. After lugging my 100W Boss Katana several times to my bandmate's house, I started looking in to floor modeler units to have something more portable. This raised a million questions I had never considered having never done live performance.
After some research I've come to a few conclusions and I want to verify if I'm thinking about this the right way before investing money into a piece of gear
There is no setup that will replicate the feeling of sitting in a studio with a high quality tube amp and cab. The "amp in the room" feel will require an amp in the room.
When listening through the same cab, speaker, headphones, or PA system, a quality amp modeler will be nearly indistinguishable from the real thing.
The final "output device" the listener is hearing from has the largest effect on the quality and nature of the sound. A mic'd up tube amp played through a shitty phone speaker will sound like a shitty phone speaker. An amp modeler through a quality speaker will sound like a quality speaker.
The place where I get confused is this: I see many people talking about using their modelers with FRFR speakers or through a cab. Is there a benefit to this for live performance? Why mic up an FRFR speaker when it's just going to the venue PA anyway? Is there any reason to not just go direct to PA, so long as you or the venue has a way to monitor (e.g. wedge, in-ears, etc)? Even if you had a high quality tube amp, the audience is likely hearing it mic'd up through the PA speakers as well. What kind of setup would provide a substantial enough benefit to your live sound that would justify lugging around such heavy gear?
TL;DR - Is there any scenario where the ideal setup for live performance is not simply an amp modeler direct to FOH?