Actually, there is a grand tradition of parks operating all night long. Well...it kind of depends on what you mean by "operating." Of course, frequently the only thing open late late at night is the lunch counter in a hotel or a food joint someplace...
But the biggest issues are necessary downtime for maintenance (note the proper spelling) and of course the need for staffing. The problem of people overstaying their welcome is overcome through the use of wristbands or handstamps with a particular expiration time on them. I know Oaks Park and Indiana Beach both have less-than-all-day POP ride pass programs, though Oaks Park seems to be a trifle better organized about it.
--Dave Althoff, Jr.
Who thinks there are places where an all-night park could work, subject to certain caveats...