Tubes are making a rebound as millenials and genzers flex their economic muscle in seeking retro tech like fine turntables and tube amps (I recently purchased a McIntosh MA252 hybrid and put in Golden Lion Russian tubes--sweet for a 2nd office system). Tubes are warm, but not as reliable as well-built solid state--technology moves forward regardless of nostalgia.
Sorry I disagree. To reduce the appeal of tube-based amplification to merely "millenial rebound and genzers flexing their muscles" is incredibly presumptuous and short-sighted. Many of us have started with SS, gone back and forth between tube and SS, and prefer tubes based on our listening preferences. It has nothing to do with making fashion statements or nostalgia.
Secondly, well-made tube amps from reputable companies are very reliable. If you choose wisely and buy from established tube vendors, most tubes are also very reliable. Of course, they have a shelf life but we all make that decision with this understanding.
And lastly, the segment for class A amps, compared to the overall audio market is minuscule and limited to a tiny subsection of enthusiasts. I seriously doubt that, given the small market share, it puts a dent in the environment. The analogy with motor vehicles is flawed and a bit exaggerated.