a) for a conversion from Bitcoin to cash?
or b) purchases using Bitcoin?

1 BTC is around $50k now.
Consider tranfering $50k to someone in a foreign country. The amount of time and fees you will pay is still way less than the fees you are paying for Bitcoin. And time? You can send it over in even less than 10 minutes. Consider this bringt side.
This is actually right and I can vouch for it since I had a transaction from Binance last year which was the biggest earn I ever had in the crypto industry. In the crypto industry, you don't need to have some complex documents where you need to prove you are the owner of those huge amounts of altcoins. All you need is just one KYC and everything is good to go and even you don't complete the KYC in some of the exchanges you can still move your BTC or any other altcoins without worry and Yeah! moving cryptocurrency is way more convenient than moving those fiats.