If you own guitar equipment such as guitar amplifiers, wireless equipment, pedal systems etc. then you might find the schematics of these parts to be a very valuable piece of information. Many times we may be in a rush to repair something that we need urgently for a performance and having the schematics can be very useful.
That being said at one point you might decide to get new equipment on a budget rather than repairing old one in which case you should look at the top picks such as the best electric guitars under $500 in the market right now.