I see this very often, and I am wondering what's the point in creating foreign key constraints in the database without actions?

In VFP tables we were used to enforce foreign key relations purely in the business logic and how the queries are built. In SQL Server, if you create fk constraints, they show the relations in the diagram. But other than that, is there a purpose for it? Unless you specify any cascading actions (which I would not like to do) does it have any advantage?