It can all too easy to forget that the film industry is a business.
Only partially in the sense that you're talking about here. It is a business and producers have a tenency to want to protect their invesments, but your big budget films tend to rely on the past successes of well known directors and more often than not, they get pretty much free reign to do what they want with a film. If things were strictly business, then studios would be doing more to appeal to the masses than they are now and not simply letting big names piss off their fans. Sure we get some focus groups these days, but for the most part, the film is going to be the director's vision. You also aren't taking into account the indy market which really does focus more on putting a particular person's vision up on the screen.
Nevermind that you could potentially make more money with a G rated movie since you're taping into a larger market…
Actually, you aren't. Films that earn a G rating aren't as common as other types of movies. Even within their own market where they have virtually no competition, the movies tend to be hit or miss in the box office with only the major studios really pulling off the hits. The PG and PG-13 audiences are definitely larger than the G audiences. Don't think that just because something is open to the general public that it is automatically going to appeal to everyone. There is a stigma against films with the G rating which limits their audiences. That's why so many studios shoot for that PG-13 rating these days. It's got enough of the violence, sex and swearing to appeal to the teens, can cover the more mature themes to appeal to the adults, but still sounds tame enough for people to bring their kids along. G rated movies tend to be seen more as the kind of movie you pop into the DVD player to shut the kids up for an hour and a half and a lot of people won't even give them a chance on the virtue of them being “for kids”. They're not “edgy” enough for the teens or “smart” enough for the adults.