Look at a crowd of people waiting to enter your haunt.
How many of them look like they jog every day?
How many of them are already limping?
How many are definately overweight and won't be moving quickly for any reason?
Ever play contact sports? What happens when a large person runs over or falls on to a much smaller person? It isn't usually "pretty".
People get older they are not a physically agile and strong as they once were.
"No Running!" (When people run, they fall down)
"No running or we will put a saddle on you and rent you out for rides to people with whips."