There's a long list of factors people may point to in an attempt to explain this. Regulators have taken a hands-off approach to bitcoin in certain markets. Dozens of new hedge funds have launched this year to trade cryptocurrencies like bitcoin. The Nasdaq and Chicago Mercantile Exchange plan to let investors trade bitcoin futures, which may attract more professional investors.
As a general rule, what goes up can come down, and what goes up particularly quickly is privy to come down just as quickly. This is not to say that things will come down if they go up, but merely that they can, and certainly have before. This is particularly noteworthy today, with ethereum having seen some truly wild gains this year, all the way up from $7 back in December of last year to over $350 presently — a gain of 50X in just about half a year. Again, this isn’t to say ethereum will fall, but merely that it very well might, for any host of reasons, and it’s very important to keep this fact in mind and not overextend yourself with investments you perceive to be less volatile than they truly are. I’ll get back to this more later.

Yet there's reason to doubt that cryptocurrency frenzy will return. JPMorgan Chase, Bank of America (BAC) and Citigroup (C) — Ma Bell in Warner's analogy — banned credit-card purchases of cryptocurrencies. Meanwhile, the SEC and foreign governments have cracked down on initial coin offerings. And lately, Alphabet (GOOGL)-unit Google, Facebook (FB) and Twitter (TWTR) have banned cryptocurrency ads.
Please note that virtual currency is a digital representation of value that functions as a medium of exchange, a unit of account, or a store of value, but it does not have legal tender status. Virtual currencies are sometimes exchanged for U.S. dollars or other currencies around the world, but they are not currently backed nor supported by any government or central bank. Their value is completely derived by market forces of supply and demand, and they are more volatile than traditional fiat currencies. Profits and losses related to this volatility are amplified in margined futures contracts.