Because it's a scam. It's used for drug dealing and the illegal arms trade. In other words dirty money. If you're happy to make money out of that then that's your business.
Welol don't use your internet search engine of choice to see what the major banks have been fined for. They're involved in a million times more crime than bitcoiners, yet none of them are in jail. Ross Ulbrecht, on the other hand, is facing life in jail for doing the same things on a relatively tiny scale. How is that fair? He wasn't laundering money for the Mexican drug cartels, he wasn't rigging LIBOR, he wasn't providing access to funds for Iran, that was the banks. So @Viviennemary, crime is mostly facilitated by banks, not bitcoin.
Your fiat currency is more corrupt than bitcoin, and is the true bubble.
According to Michael Pento (GIYF), the banks are likely to go tits up late this year. But then again, he's trying to flog his hedge fund so...
Ronnie Moas reckons BTC could hit $40k this year.
I have a theory on Crypto based on my interpretation of part of a speech a couple of years ago by the BoE economist which I'll expand tomorrow. Too tired now.