This is good for whole scene lets say day and night (by the way thank you I will need that too 
), what if I want to change chair in just one part of house, its not practical to built light for whole scene just for chair, I mean you can but its tedious job. In 3ds max there is sphere of interest (have no idea how it is called) and it render just what is inside of it, something like that would be good in UE (there is also other shapes as far as i remember)