Some classes of human,Sometimes when they are to receive money from another country like international transfer sometimes it takes 2 3 days to arrive,They will advise them to use bitcoin and they still don’t accept it even it faster and easier.
It's faster for sure, but what if the person wants to be sure that what is being send is exactly worth $1,000 for instance at the time of converting, with Bitcoin being volatile you can not be exactly sure that the price stays at the same level after you waited for network confirmations and the time it takes you to convert it to your national currency to be able to use it.
That being said that doesn't mean you can not use Bitcoin for international transfers, I totally agree with your points you're trying to make, but the thing is it depends on the use case of those that are sending money internationally too, and while you and many other could be totally okay with some downsides that crypto transfers could have such as volatility, some other may not, also don't forget the fact that many still largely unfamiliar with crypto or even consider it as exit scam waiting to happen to this day.