The end of tube amps?
Tube amps used to need to be loud. First (big band jazz) to keep up with horn sections, and later (early rock) to fill the room w/o PA support. PAs of the era barely kept the vocalist(s) at parity with the guitars and drums; forget about trying to run a full mix through one...
Disco (from the early `70s right up through modern dance music and techno) and corporate rock (big stadium shows of the `70s) spelled the beginning of the end. Those were the drivers for big sound systems. Demand drove down the price to where a small-club owner could afford to buy or lease a pro- or semi-pro system.
Once the club market for big sound systems became saturated (and it certainly is here in Portland), the supply of gear had to go somewhere. Yup: churches.
The few churches I've been in (none during a worship service, unfortunately… something about insurance and lightning… ) have had pro-grade sound systems that'd make any of Portland's small club owners envious.
I want to be clear that I do not find fault with that in any manner whatsoever. Anything that encourages people to worship - to look beyond themselves - is good with me. I was raised Catholic (now a spiritual agnostic or agnostic theist) and can tell you that masses in Latin and boring sermons certainly didn't grab the attention of most of my generation.
Along with the big sound systems come their operators and a certain aesthetic that attempts to impose high production standards upon the performances. In a small room, that aesthetic demands (via the laws of physics, more than anything else) low stage volumes. A tube amp simply does not play well in that environment.
If the sound operator wants to keep the volume to a sane level (and I wouldn't be surprised if they think about things like the SPL versus safe exposure time), a guitar amp - even one of less than five watts - is probably going to not only ruin the mix for the audience in the front (and maybe even quite a way toward the back, depending upon the size of the room), but will also annoy the heck out of the vocalists and the musicians who aren't playing screaming-loud instruments.
You can tame a tube amp for that environment through use of ISO cabs or rooms, but that kind of ruins the experience for the guitarist. Hearing your guitar played into a screaming amp through a stage monitor or IEMs just isn't the same as standing in front of the amp...
Furthermore, all of the paraphernalia that you have to lug gets to be ridiculous. Tube amps are bulky and heavy enough without all the add-ons. Start carrying baffles or and ISO box and you'll quickly wonder why you bother.
Ditto for trying to dial down your amp's volume by 20 dB or more using an attenuator, except it'll be the resulting sound - and not the bulk of the gear - that turns you off to that tactic.
As I said before: If you have to play in small-ish venue on a fully-mic'd stage, good luck making a tube amp work for you.
OTOH, if you're playing large venues or festival stages, bring it on! This is where tube amps shine. Again, it's the physics of sound that allows a tube amp to coexist with a PA in a large venue.
Everything's going quieter. The instruments that are getting all the attention now - samplers, keyboards, laptops, synths, even e-drums - are all electronic. They're perfect for the production-oriented world of music, as they contribute no stage volume to interfere with the perfect FOH mix. Guitar amps - not so much... They're dinosaurs in a world of flying cars.
If you play by yourself or with your buddies in a room where you're not going to get complaints about ear-splitting volume - and don't care about the health of your ears - then by all means crank up your tube amp. Or if you're playing big venues or festival stages, well... you don't need my advice.
OTOH, if you want to play in small venues with full PA support and sound good, then do yourself a favor: invest some money in a good modeler and a decent FRFR system, and learn how to make that rig sound good at a sane volume. Your ears will thank you, your sound guy will thank you, and your audience will thank you.