Not really. Tube amps provide certain sound effects that electric guitarists consider desirable - tone, a little bit of drive/distortion, and I think a little c

Not really. Tube amps provide certain sound effects that electric guitarists consider desirable - tone, a little bit of drive/distortion, and I think a little compression. So you can plug an electric guitar into a regular old PA system and it will make some sounds, but it won't have that desired tone and the listener might not think that it sounds very good. You can compensate for that by putting an effect pedal in the middle the simulates the sound of a tube amp, and of course the solid state amplifiers that professional guitarists use these days have that effect built right into them so that they sound good out of the box, but notice that the question has now changed from "why do people use a tube amp" to "why do people use real tube apps when simulated versions are possible"? The tube amps that people use are well known and well liked, and while it's certainly true that there are solid state amps that sound good, these days, too, it's not like they are categorically better than tube amps in any way (yet?)