G movies will always have the higher probability of drawing larger audiences because they can pull from a larger population of people. That and of course if you want to clam your kids down for 90-minutes you don't take them to the new blood and guts horror movie, the drama which puts them to sleep, or the techno triller that they couldn't follow unless you updated them every 5 minutes.
They are not comparing apples and oranges - they’re comparing dollars and dollars - and, since family friendly movies get more dollars, so why don’t they make more?
The answer is “Because they don’t want to.”
So the real question is “Why doesn’t Hollyweirdstan want to make more profitable family movies?”