Comment by hashmash

This adds an extra level of friction that doesn't happen when the set of primitive types is small and simple. When everyone agrees what an int is, it can be freely passed around without having to perform special conversions and deal with errors.

When trying to adapt a long to an int, the usual pattern is to overload the necessary methods to work with longs. Following the same pattern for uint/int conversions, the safe option is to work with longs, since it eliminates the possibility of having any conversion errors.

Now if we're taking about signed and unsigned 64-bit values, there's no 128-bit value to upgrade to. Personally, I've never had this issue considering that 63 bits of integer precision is massive. Unsigned longs don't seem that critical.