Sometimes it's just not a good idea to open the door when a stranger is ringing the doorbell. (OK, it's never a good idea to open the door for a stranger.) Sometimes even peering through a window or opening a curtain to see who's standing on the other side of the door is not a good idea. And yes, we admit it -- sometimes it's just too much of a hassle to walk across the house to see who's there.
Video intercom systems let you get a good look (and even a listen) at visitors without having to get too close. They also provide crucial distance and time if the caller does not, in fact, have good intentions.
So if you'd like to put another level of security between you and the stranger at the door, a video intercom system is the way to go.