Incrementing an ID requires complete knowledge in a single place, which at scale becomes a challenge. This would typically be done in the database, but doesn't

Incrementing an ID requires complete knowledge in a single place, which at scale becomes a challenge. This would typically be done in the database, but doesn't bode well with distributed systems as multiple servers might thing "5" is following "4" leading to multiple rows identified by the same ID => this is a collision. So UUIDs are great because multiple servers can generate plethora of them without having to worry about collisions. This is all explained in the first few pages of the document, although not in simple terms. Also I haven't spotted anything about UUIDv6 trying to avoid collisions, but I haven't read very far.