Because the government initially did not prefer bitcoins as they were highly volatile and if there are any crimes that take place like money laundering it would be very difficult for the government to trace them. Although both the problems are not solved one of them does seem to be. If the price stabilizes it is likely to attract more people to use them. So I guess that the verdict in December by the SEC will legitimize bitcoin at least in the US in case they rule in favor of cryptocurrencies.
LOL it won't be stable for 20 years. If it's the internet of money, there is a lot of growth and wealth to be stored in this technology.
Even the SEC allowing hedge funds into bitcoin, that just means the holders with billions of dollars can make the volatility continue forever if they really want.
The graph will still go up over the long term.