A very simple statement may not be as simple as it looks to execute.

The table here is unconstrained (from the article "CREATE TABLE integers (value INTEGER);") but suppose that table had a primary key and a foreign key – a simple insertion of a single value into such a table would look trivial but consider what the query plan would look like as it verifies the PK and FK aren't violated. And maybe there are a couple of indexes to be updated as well. And a check constraint or three. Suddenly a simple INSERT of a literal value becomes quite involved under the skin.