Crypto currencies are the future, not now and maybe not in next 50 years but a time will come where we will pay digital only. Take a look at Paypal for example, it is comfortable and today really convinient to pay with Paypal and even Skype now implements a payment service (I never sayd I trust Microsoft ). I agree to all the backdraws that come up here saying that all for primary Bitcoin as the dinosaur of CCs has massive problems but I wont see it as the future of payment rather than a toybox so one could experiment and extend the technology for a Bitcoin 2.0 however it will be named then.
I study CCs for a long time know since 2014 (and yes this is ages in technology) and I saw the evolution, anonymity, more anonymity, even more anonymity and mathematical improvments to make data blocks smaller and security higher. The core technology is very interesting to me.
The pros are uncontroversial there while the cons are there too. The most given argument is that CCs at the moment arent very stable in value but to solve this we should first take a look at the history of money. People found/harvested something (I may remeber it were shells as the first really trading value) that other people also liked to have and trade other goods and services for. It became convinient because you wont be in the need to carry a chicken anymore for trading that against something else over a long road and back home; letting other new business grown up like merchants or money changer (that later become banks)
Complete History of Money
I see this as the primary advantage of any CC regardless how it is implemented at the end, that people can carry there values without any major drawbacks. You wont need a bank account anymore (what I think is the main reson that CCs will not establish so far because companies earn money with your money) that disables the need for storing fees you have to pay. Without a bank account you also wont need an address that is why some homeless people cant get work in our countries (you need a home to get a bank account to get a job to get a home = fail!). Ever payed for bank card, print your own ones with CCs. It dosent take time to change your account like two weeks for the traditional way, it does just take a few seconds and you are done. Payment (could be) as fast as hell, while you have just to scan a QR code on checkout and your partner in contract gets nearly instant message about success or failure while you can also pay at weekend or holiday out of the usual business hours.
Transactions are as safe as the crypto problem is and unless someone invents the quantum computer, they will stay so (while even with our other currencies will get unsafe with a quantum computer) and anonymous if used correctly. This might be a point where people will discuss about but my opinion is that government should not know about what/who I pay nor has it the right to denie access or steal my money for whatever reason. Tax crime is a problem today but I dont think it will be a greater problem in a CC scenario. People will then just be forced to make a tax sheet what most companies and self-employed persons are need to do anyways so government can still check for tax crime while no-one other can investigate a persons payment history just from the blockchain.
Evaluating payments costs energy and so money this is fact but also fact is that any other of our digital payments today costs energy as well. But with a CC based payment system people offering computing power could earn money and so have the flow of currency units never stopped. I calculated with a fixed ammount of transaction fees that are measured not on value but on size of the transaction. It is not the transaction value that consumes the power but every block of bytes so why not pay per block where a block is big enougth to hold the information for one payment plus a bit extra. Larger payments or bigger payment bundles will then be at a higher cost because they take the space of smaller payments while transfering other values, for example contracts would also cost a bit more. I would give that money however to the evaluating network node to give an appeal to the human kind to take part at the system. However the crypto problem should be solved on evaluation, it should be fair and I also think we need multiple evaluations in parallel to get all the payment traffic done in the future.
I think the above can also help keeping the value stable because currency units are always in flow until the whole system stops working while I agree that the CC value should be something physical too. It is right that countries print there own money and print more money as some of them might have in gold and other values. Occasionally a reason for countries to make debts and get into insolvency. The backdraw on Bitcoin was that when the blockchain starts the first time, the inventors of Bitcoin should have taken a huge ammount of coins for themselfs before going into real public traffic. I thought about it and in my opinion there should be an initial fixed value of currency units equal to the financial value of a country spread to each country taking part at the system. So you will never ever have more units as are sealed by the value of a country. Countries give there currency units to citizens and may give or take currency units to keep the currency stable.
There are also a little more problems CCs have to solve in the future but I think this hits the core discussion