This is incredibly naive. Many second year EE students today will not even know what a vacuum tube is, much less be able to explain how a device using them works.
Even if you're used to looking at discrete transistor circuits (and even that is getting rare these days), a device with tubes can look like magic of the highest order.
Seconded. Another factor is that looking at a device won't tell you why it was designed the way it was. A good technical manual will be invaluable for telling you things like valid ranges, service or environmental limits, etc. which would otherwise need to be reverse-engineered. If you're trying to replace an old system or studying the history, know what does and doesn't matter can save a ton of time.
(This goes double if the manual was annotated by a good operator)
Tubes are history, so you pretty much agree with me? :) I didnt say those manuals are unimportant and should go into the landfill, I pointed out they are of historical nature, not something you would actually use today.
Even if you're used to looking at discrete transistor circuits (and even that is getting rare these days), a device with tubes can look like magic of the highest order.