Here are a list, in no particular order, of things discussed in other threads that I think count against cryptos:
1. No government backing, cannot require tax authority or judgment creditors to accept cryptos
2. Not widely accepted as currency by merchants
3. Deflationary, money supply cannot easily be expanded when determined necessary by central banks
4. Treated as a capital asset for IRS purposes (transactions require basis recording and reporting, so cannot be easily used as cash)
5. Wildly volatile
6. Cannot effectively loan most cryptos
7. Not subject to seizure based on court order, so cannot easily be used as collateral and loaned against
8. Can be forked at any point in time, leading to confusion of contracts based on pre-fork crypto
9. Lost private keys means units of cryptos can be lost forever
10. Hacked exchanges happen all the time, and hodlers at exchanges are not fully insured against loss
11. Incredible, growing energy consumption needed to mine
12. High transactional costs needed to get miners to process transactions
13. Not truly anonymous
Full disclosure, I mine ETH and XMR, but I'm mostly a cryptocurrency skeptic. In specific I have never purchased any as an investment (I own a little BTC that I purchased to buy goods online). A couple responses:
1. I can't pay my US taxes with Euros either, but people have been trading currencies for centuries.
3. I think that you are completely correct, cryptocurrency is more like digital gold than a good stable currency.
4. Yes, just like any foreign currency.
5. Sure, see #3.
7. I think that you are wrong on this one. If it needs to be used as collateral, why not transfer it into an escrow wallet? Just because no one is doing it doesn't mean that it can't be done.
8.
This is a very good point9. Sure, print that shit out and store it in a safe deposit box. What happens if you lose your physical gold?
10.
This point is pretty solid, I think it is one of the large problems with major adoption.11. Ethereum is trying to solve this.
12. ETH is ~$0.80 right now, to transfer an arbitrary amount of money to an arbitrary location on the planet that seems pretty good?
13. I am not an expert at this, but Monero and ZCash are trying to solve that. ZCash in particular is using cutting edge "zero knowledge proofs."
I would like to echo a couple of your points above: there is a security/accessibility problem with cryptocurrencies at this point. You can keep everything in an offline wallet, but then it is hard to spend. You can keep everything in an online wallet, but then it is easier to hack.
I would also like to add my own:
14. As a retail investor, it is easy to buy a broadly diversified equities portfolio through any number of mutual fund companies (95% of my net worth is in VTWSX). The same can not be said for cryptocurrencies. Even if we accept that cryptocurrencies have utility and/or value, that doesn't make them a practical/good investment for the average retail investor.