"This is John Crichton... somewhere in the universe."
Anyway, I think that the reason John hasn't used his tape recorder since Family Ties (which is easily the best episode ever, IMO), is because he left it on "Record" during his farewall speech to his father. He never turned it off. Therefore, he ran out of tape for it. And it must be rather hard to find tape for a microcassette recorder in the UT. And John probably didn't want to record over anything he already said.