Most people have cameras mounted on the house facing out. Some will also have a camera facing towards their door in case they hear someone at the door or if a package was delivered. That camera is for my front door/packages.
I think it really depends on the threat assessment. If you live in an area with low crime, then it probably isn't needed. However I would absolutely try to have this coverage in a high crime area, especially if my house appeared to be nicer than others around it.