90% of the reason tube amps live on is because all the cool kids use them because the cool kids are in bands and tube amps are easy to fix. A dozen tube types and a good supply of resistors and capacitors is all that is needed to fix most tube amps which means you can get your amp fixed asap at any repair shop, common parts they all have in stock. With solid state there is a very high probability that parts will need to be ordered since no one can keep the very large number of possible parts those amps use in stock so you end up buying a new amp to finish the tour with and ship the old one home or abandon/sell it.