"...backed with nothing tangible..." What is the dollar backed by? What about in 2008 when the banks collapsed, and people couldn't get their money out of the banks? Government issued fiat currencies haven't been backed by gold in decades. Government bonds maybe? But it being backed by government bonds means it's only supported if the bond has value, which is directly related to whether the country itself is doing well or not, and ultimately, that is using the peoples' money (tax money) to back a bond of the peoples' money - which is circular logic. And it's directly related to whether the government is functioning properly and in the best interest of its people or not (see Venezuela, Tanzania, the rest of the failed nation states in the world, etc...). When people (justifiably) have zero faith in their government, crypto becomes the currency of the people. You could argue that government fiat is backed by military might, but I prefer the idea of a currency that doesn't need to kill people to maintain its value.
"...what country wants this?" Crypto isn't made for countries, it is made for the people. Bitcoin specifically was made as a response to the governments of the world bailing out corporations instead of people in 2008. That said, Wall St is begging for regulatory framework so that they can jump into this sector, and the head of the IMF recently told the banks of the world to explore ways to get into crypto and utilize the underlying technology. And there are near daily patent applications by banks relating to crypto. Many countries are looking at making their own cryptocurrency to replace their physical fiat. Cash itself is becoming increasingly rare in the developed world anyway. Try withdrawing $10,000 from a bank in cash and you'll have to wait a few days, because the banks generally don't have it on hand to give you.
And crypto is much bigger than Bitcoin... 3.5 billion people in the world are unbanked (don't have access to banks, banking services, etc). Crypto will bring those people into a world economy that doesn't need banks (because a cheap cell phone with NFC can operate as a crypto bank capable of doing transactions), with currencies that aren't beholden to the meddling of governments that drive inflation through bad policy or antics, or centralized banks that just bilk the people by charging interest on each dollar they create, enslaving nations under mountains of debt that can never be repaid.
"The biggest beneficiaries of Bitcoin et al are cyber criminals." Sure, some users are criminals, but the percentage is FAR less than the percentage of criminals using cash. 80+% of physical dollars have cocaine residue on them. Pallets of cash get flown all over the world to be used to bribe warlords so that they will support resource wars by foreign governments, while ignoring what those warlords do to the locals. Cash, central banks, and governments have FAR more blood on their hands than Bitcoin does or ever will. Or real estate - the biggest method of laundering money in the world. If your moral stand against Bitcoin is that criminals might use it, then you probably shouldn't use cash, and never own property either. (Meanwhile, crypto has created millionaires and billionaires, many of whom have moved to Puerto Rico partly because of its tax break status, but also to help rebuild the island's infrastructure since governments have so miserably failed them after the storms ruined the pace a couple years ago. Crypto users tend to have a pretty altruistic intent. They're the people that see government misspending trillions while people starve, and they're choosing to try and do something about it, using technology.) Bitcoin isn't anonymous anyway, so anyone using it for criminal deeds is a fool.
There is a ton of value in cryptocurrencies, and even more in blockchain, to change the way the world works at a fundamental level. Personally, I'm excited by the idea that over half the world's population will be able to join the world economy; that cryptos are not owned by countries or central banks making them non-debt based currencies like fiat, and the idea that blockchain voting systems can make governance completely transparent and democratic while holding governments accountable.
At the risk of sounding rude, if sounds like you have been pretty misinformed by people with an agenda (mainstream news) or people who simply don't know what they're talking about, and I would encourage you to watch any YouTube videos you can on guys like
Andreas Antonopoulos (or Vitalek Buterin, or Dan Larimer) to get up to speed on this sector before you miss out on one of the biggest revolutions since the Industrial Revolution or the birth of the Internet, because blockchain and crypto are potentially that fundamentally transformative.
Regulatory framework is coming to crypto which should level out the huge swings in the markets, and lead to more organic sustained growth. In the meantime, there is lots of money to be made in the volatility. I think it's a great time to buy into any of the top 15 projects. I'm sitting on my holdings for a couple years just to see where they go. Last year was 1400% gains for me. 2018 clawed a lot of that back. Market cycles suggest 2019-2020 will be bigger. Time will tell.
(And I'm someone who doesn't like Bitcoin. That doesn't mean I don't think it'll go up, but I don't currently own any. There are FAR better crypto projects out there in my opinion.)