How do you explain that the amusement parks don’t just shutdown during their slowest days or time of year?

It probably does not come as a surprise that the worst days of the week to visit the theme parks such as Magic Kingdom are Fridays, Saturdays, and Sundays. Other poor choices include long weekends and popular holidays. These are times when crowd levels are at their highest. Likewise, theme park attendance is seasonal, and January and September are usually the least crowded months.* However, while the crowds may be smaller, there may be shorter overall operating hours for the park, fewer show performances, and there may be fewer operating trams between parking lots or resorts and the park entrance. How do you explain that the amusement parks don’t just shutdown during their slowest days or time of year?
This youtube video shows you how to Avoid Long Lines at the Amusement Park–(https://www.youtube.com/watch?v=HwNy7JpgWHg)