prosfilaes
Adventurer
I'd consider "low-pro" to be a one-or-two person company that didn't or can't get products on brick-and-mortar store shelves. There are maybe a handful of companies that _won't_, but there's a lot that can't. That doesn't mean they're not professional, but they're not big leagues. I think that's a hugely relevant group of publishers. Without them, you're talking fan creations or established publishers. I also disagree that putting some polish on a product is a sign that you want to "hit it big".
Lotteries rake in billions by banking on the idea that most everyone wants to hit it big. You'll get a lot more people by letting them dream then by cutting them off at the start, especially when the lottery would usually be a more profitable place to put your money then most RPG development.
As to why someone would do it...well, there is no license and Frog God Games is already planning three books. Why would they do that? Obviously for the audience.
But they're also not worrying about the license. They can, or feel they can, push books to game shops. They don't believe that WotC can cut off the license at some point.
That doesn't mean I think it's going to happen.
I think WotC putting 5E under the OGL is incredibly unlikely. But I don't think that any very restrictive license is going to help them, and with people like Frog God Games publishing without a license, a restrictive license may encourage people to publish without a license.
I've yet to see a convincing argument that the OGL would have made 4e a better and more accepted game.
It couldn't have hurt. Some publishers that shut their doors or changed their tactics would have started publishing for 4e. The decision to make their own system would have been much harder for Paizo if they didn't have problems with the GSL. If Pathfinder didn't exist, 4E would almost certainly have been more accepted. If Paizo did create Pathfinder, at least there would have been more 4E support.