The last thing you want while lounging in your living room or while asleep is an unannounced guest. At the very least, you want to know who or what is entering your property. This is especially important if your driveway is a bit of a stretch from your house such that anyone can come in without you noticing, especially if the visitor happens to be an intruder who is up to no good.
You want to feel safe, don’t you? Of course, you don’t want an unannounced visitor showing up at your door with such flimsy excuses as “I was in the neighbourhood and I ….” or “the gate was open, so I let myself in.”