Why tubes? Why are there more tube amp manufacturers today than at any time in history? Why has there been such a resurgence in analog and tube electronics?

That tubes sound better is not so much a matter of "if" as "why". Some say it's because tubes produce harmonics like real instruments do. Harmonics are the overtones that make a piano sound different from a violin or trumpet. Tubes produce overtones that are even (2nd, 4th, 6th) just like musical instruments. Transistors produce odd overtones (3rd, 5th, 7th), which aren't "musical". Some say that tube amps don't have the same perfect frequency response of transistor amps, and tend to lessen high frequencies while producing a "fat" or "wooly" bass sound which is pleasing to the ear. Well, some do and some don't. The transformer is usually the cause of this, but a properly designed and built tube amp will have a fine frequency response. There are also several fine OTL (Output TransformerLess) amps that not only equal, but soundly better the quality of almost any solid-state amp on the market. There is also the fact that when driven beyond their design parameters, tubes clip in a much smoother fashion than do transistors. That is why guitar amps use tubes, because they sound better when overdriven, and behave better electrically as well.