Yes, the park are coining it in on these events. I personally couldn't give a monkeys about the fireworks and would sooner the rides ALL stay open til 10pm on these nights, even til midnight like they did up to a couple of years ago. I think the posters are somewhat misleading people by promising 'LATE NIGHT RIDING.' I guess it grabs the attention and is more catchy than 'INTO MID EVENING RIDING', but really, would anyone consider 9pm to be 'late night', as so many rides close at that time?
Shakey, as regards 'it keeps people in the park til the bitter end', people will leave whenever they've had enough. I must be getting old but I retired to the Big Blue hotel around 9 to watch the fireworks (yes, the very ones I just said I don't give a monkeys about!). I simply couldn't be bothered with one more hour in the park with most of South park area rides shut, Wild Mouse shut, Flying Machines shut in the wind, and having already been in long queues for Nash & Dipper night rides, couldn't face them again (to be fair they were moving fast other than breakdown on Dipper when we were about to board).
I get the tactic from a business point of view: Close half of the rides, thus making the queues huge for the remaining ones, making people give up and flock into the outlets buying food, drink and merch whilst they wait to watch thousands of pounds being blasted high into the Blackpool sky never to be seen again. I'd just rather see all rides open to the end.