Timestamps, UUIDs, and such have no dependency on a central source (and thus, single source fo failure) for generating them. Much better scalability. Even with

Timestamps, UUIDs, and such have no dependency on a central source (and thus, single source fo failure) for generating them. Much better scalability. Even with a single server, not relying on IDs being sequental is useful when you want to do a database migration without temporarily shutting down the site. It is much simpler to merge the two databases together.