In Hamlet, why does Polonius send Reynaldo after Laertes?

This is whathas
to say about that: What was I about to say? By the mass, I was about to say something! Where
did I leave?  In other words, not even Polonius really knows why he sends a spy. There's no
special or good reason. Instead, we must look at what that shows us about him and the court: he
spies on his children out of habit, and distrusts them automatically, assuming he knows best.
This shows us that the court is a place of distrust, though not, ironically, where it needed to
be. ( didn't suspect his uncle in time to save his father.)