Using integer primary keys often creates race conditions (that result in collisions) when you have multiple database shards, so UUIDs have become the standard. (2 different webservers can create a record in 2 different database that then sync with eachother in the background). Using UUIDs for SQLite is less common though as SQLite is mostly used for small or local applications, but developers are used to UUIDs now and even consider them the standard for primary keys now so you do see them in SQLite databases. (Oh and there's some SQLite compatible sharding servers too)