Real problem with bitcoin or Ethereum or any other VCs out as of this date is that there is no underlying or backing of any asset for VCs. As such, their value seems to be a matter of speculation. Huge volatility in the value of VCs has been noticed in the recent past. Thus, the users are exposed to potential losses on account of such volatility in value.
No expert can predict it is just a bubble or prices are really going up backed by strong fundamentals. Many consider share market a risky ride but if you compare share market and if my memory serves me right then the biggest change is 5-5.5% in a day whereas bitcoin has seen around 28% fluctuations in a day. *Just think and answer it to yourself how many bumpy rides you would have survived both in bear and bull phase ?*
Moreover as there is no regulatory authority so if you lose bitcoins anyhow hacking, forgetting password, or one day supporting app/wallet/exchange decides to keep some of these citing some hack or some technical problem then you just lose them as you can't approach anyone like any authority like bank, RBI or Sebi. All of the aforementioned scenarios happened in past.
Remember the saying of Warren Buffet Invest Only in Companies/businesses you Know and you trust `An investor should act as though he had a lifetime decision card with just twenty punches on it.`