Programmers who are not aware of the pitfalls will use the sync version and build apps that have terrible ux, so it’s better to not give them the option unless there’s a really good reason to, so what’s the use case here?
How would you "handle the async" at a different layer? If you were to call sync crypto methods, they'd block the event loop no matter where you call them - unless you call them from a Worker, at which point they're async calls again.
The only real use case would be small scripts where you don't care about sync/async, but experience shows that devs will abuse the sync functions in scenarios where the async ones would be appropriate.
