That serves a purpose, though. Relaxing after work is perfectly legitimate. Having an investment scheme where you issue numbered bank notes and agree to never use a bank note with a number higher than 21 million, then track on some forum who now owns which bank note, would work the same way as Bitcoin. So long as people keep buying, the price keeps increasing, as it does with Bitcoin. Except that Bitcoin also agrees to burn some Terrawatts for no added benefit.