Lawns are one of the great Cliches of American culture. I'm no fan of grass. Too much space is wasted on uncreative and high maintainance landscaping. There are many groundcovers that need little water, need no mowing, and yes, will grow in sand. A lot of prairie species do well in dry sandy areas. The barren ground around some rides does bother me but who says that they have to swing through a perfectly manicured golf course? Gravel is a bit of a cop out but it does have a place for areas under rides that need periodic access and where too much trampling would kill the groundcover. I guess one concern is vegetation growing too high and interfering with the ride's operation.