One beneficial use case from the US perspective is further global dominance of USD (if you are into that sort of thing). This limits the ability of corrupt governments from inflating their fiat, which is generally a worse currency than USD fiat.
How much was paid in fees in total, from your currency to theirs (I assume VND)? If it's a USD stablecoin, I assume they still had to convert it to VND, or at least they'd have to if they were paid mostly like this (to pay their taxes).
Wise and others are quite cheap for the currencies they support.
A lot of the Chinese crypto engineers (of which there are many) are paid in USDT. This avoids all of the capital controls and knowledge the state has. There is an entire subculture of Chinese who operate their businesses in USDT, mostly digital ones but it has bled into the physical world as well. In Hong Kong duffel bags full of paper currency would be swapped for USDT by various money changers.
A lot of people look at crypto and see what’s on the surface. The easy, instant movement of essentially unlimited money without government oversight and intervention is scaring many authoritarian governments. See the total ban on crypto by the Chinese dictatorship.
So. Illegal movement of money.
Prior governments worldwide sanctioned human slavery and collected taxes on slave sales.
You say illegal - but I say immoral
Projecting your own opinion on morality or legitimacy doesn't change the fact that taxes need to be paid, and in fact dictatorial regimes tend to frown upon tax evasion, so your opinion may also contribute to the increase of "people locked for life" just because they took you seriously. So, in some way, these stances actually contribute to the worsening of the issue.
There are innumerable reasons why someone in an authoritarian regime would prefer to earn a living outside the political apparatus, which in the current official monetary system is impossible.
But with absolute government control over the payment rails, such activism is impossible without a sword over your neck.
Also, Russia is being sanctioned through freezing their USD accounts and imposing financial sanctions such as suspension from using SWIFT.
If crypto is more wide-spread, then it will become more difficult to impose such financial restrictions to Russia and other international pariahs.
I never said to outlaw crypto or paper currency but I just brought-up that crypto is just a tool that can be used against and for such governments.
Which covers use-cases like sending money for medicine to your sick grandmother in Iran.
Not all laws are just and a world were no laws could be broken would be a nightmare.
That’s what the involvement if a central bank/state gives you.