A friend wants to visit a country and they were enquiring for proof of funds for him to be issued a Visa. This young man has invested heavily in Bitcoin and other cryptocurrencies that he might not be able to present the minimum amount they want in his fiat account. But he can present ten times more than the amount the embassy is asking if they want it in cryptocurrency.
The embassy is insisting that although Bitcoin is legal in the country, they cannot accept it as proof of funds. The guy is a little bit frustrated because he is been forced to sell his coin prematurely in other to present the amount they are requesting. The visit is for an important business where he needs to test run and evaluate some equipment he wants to acquire. Taking a loan might not be appropriate since the embassy wants to see the flow of cash and not just a lump sum.
If your friend holds ten times more amount than the embassy is asking for, then your friend should logically have enough cash for a small trip. It's a business trip after all, isn't it? A business trip.
Selling some part of his holding and presenting it in fiat would have been the easiest pathway. But we are all aware of how the market is now. Selling now is not a good move since the price of Bitcoin has dropped significantly. I don't think he would consider such an option.
Now you got the answer to your question. Crypto is volatile and that's why countries don't accept it as proof of funds. Your friend will be forced to sell some part of his crypto if he has no other cash or borrow it from a friend/relative.
these visa's are not about proof of wealth, these visa's are about having funds available on hand(easy access) to cover your visit so that you are not deemed as someone entering the country looking for work..
its also about avoiding someone coming to the country to then become a economic asylum seeker.
its also about avoiding someone coming in with funds obtained from criminal enterprises
in short, if someone cant afford to have legally sourced fiat on hand to take the trip, then how are they going to fund themselves during their stay
(you actually need money to spend on food and hotel so obviously you need to cash out some coin to pay for your visit)
You described their purpose exactly and in details but to be fair, this is stupid. People still manage to start work in a foreign country or become an economic asylum seekers. They work illegally in factories or in farms and get better payment than they would get in their homeland. I have a friend who lives in Ireland and I know from her that people cut their passports and flush it in the toilet on Airplane and then somehow the government of Ireland accepts them.
I think that the world would be better if there was an accent about quality, educated and active workforce. It's very easy for a totally useless refugee to come in EU country but it's hard for those who are good workers and simply want to have a better salary by working in rich countries.