I blame RDBMS-centric thinking. Things that look like numbers will perform well in an index, and we get free ID generation, so... why think about hard things,

I blame RDBMS-centric thinking. Things that look like numbers will perform well in an index, and we get free ID generation, so... why think about hard things, just throw it in there. In terms of identity an ID is never a number, always a unique value. It should be its own type.