What's the point of roasting a whole chicken?
The reasons people still roast whole birds are:


Roasting a whole chicken is easier than butterflying it. While it's not tough to butterfly a chicken many people don't know how, or don't want the cleanup
It's less prep time to roast a whole chicken. If you are busy you can have it from the fridge to the oven in less than a minute, while butterflying or jointing it isn't super-quick
Aesthetics: some people like the look of a whole chicken on the table