I can't add much value since everyone else has hit the nail on the head, but can you imagine if routinely all available E+ was just given away freely? The people who paid for E+ would be annoyed. The people who didn't get the "free upgrade" would get annoyed. The system is fine the way it is. Pay for what you want. At 15 minutes before departure or whatever, any seats left go to the hardworking people that work for the company.