gonjah wrote:

He should just have them "on" the door but the security door will stop
the majority of burglars that want easy access to the doors.

Think about it this way: You see someone hauling a large screen TV out
of a window or a door; which one looks more suspicious?

They also give you breathing room when you answer the door, so a criminal
can't rush in when you open the door.

They also reduce the intrusion level of solicitors (like Mormons/Jehovah's
Witnesses/*PIRGS) who blithely ignore a "No Solicitors" sign and bang on
your door anyway.

Jon