Why do experienced SQL Server DBA's qualify examples with the default schema dbo?
MS SQL Server uses a fixed search order for unqualified names (the user's default schema, and the dbo schema). So if you do not want your queries to depend on that what the user's default schema happens to be, you always have to use schema-qualified names.

In PostgreSQL, the schema search order can be modified dynmically. The documentation says:


  Qualified names are tedious to write, and it's often best not to wire a particular schema name into applications anyway. Therefore tables are often referred to by unqualified names, which consist of just the table name. The system determines which table is meant by following a search path, which is a list of schemas to look in.


In other words, the Postgres schema lookup mechanism was specifically designed to allow omitting schema names in most queries.

(The default Postgres search path is "$user", public, which is essentially the same as that of MS SQL Server, and can lead to the same problems. But in practice, the default databases privileges do not allow users to actually create their own schemas.)