Seems a shame too. Look at 10000 that has 4 different possible values.
For sure, I'd like it too, if each function would add its respective prefix, but it would break compatiblity with legacy code. But on the other side HEX$, OCT$ and now BIN$ belong to the same type of function and should behave the same way, that's why I didn't add the &B prefix.
From a different point of view, &B is a new addition added in or after v1.0, that's basically the reason why QB64 misses the built-in BIN$ function. So if BIN$ is QB64 specific, shouldn't it be _BIN$ intead? And what do we do with the binary prefix then, _&B ??