You are probably correct in the three you listed, but perhaps I can add one more.
I feel that the Open is an excellent way to promote the sport of bowling. Sure, most bowlers who enter the tournament have zero chance of winning(realistic or otherwise), and at best will only earn "lunch money" for their effort. Most of these bowlers will also be donors in the brackets as well. However, as a bowler who is somewhat new to the sport, it has an allure that I always enjoy.
I went to my first Open in Las Vegas and loved every minute of it. I have not missed one since and organize multiple teams to bowl as a group. When it's in Reno, I try to get bowlers who have never been before so they can have the experience of the tournament. For the most part, the new bowlers are thrilled by the entire thing, even when they don't win anything. It's the experience they value. I have heard the phrase "Thank you for inviting me, that was so much fun!" many times and almost always by bowlers who won nothing. Of course there have been some others, usually the "elite" who walked away with the obvious sad face of a bruised ego too.
As bowlers get better, there seems to be some kind of mental change that comes over us that actually hurts the sport. The "elite" bowlers tend to get a condescending if not not downright destructive attitude about the lower average bowlers. Ironically, the Open helps put that in perspective, at least when it comes to the local house hacks. The oil pattern they put down is not that big of a change for Mr/Ms 150 +/- average, but the hotshot 200+ "king of the hill" house bowler, it's a serious comeuppance.
So, is the Open a chance to crown champions? Yes, it is.
Does it serve as a revenue source for a cash strapped USBC? Yes, it does.
Does it educate bowlers about how difficult sport shots can be? Very much so, especially the ones who have come to believe their local fame is worthy, but never step outside their local house.
I still believe that it's the best promotion for the sport and an experience that all league bowlers should try at least once.