There might be some rocks in the sand and the kids could bruise their feet or knees. The same thing with the wooden playscapes that are now plastic. Too many splinters from the wood, so everything changed to plastic. The bad thing is that the plastic breaks after years in the sun and cuts the kids.
It's for the "kids".
Problem is, most plastics ALSO get blistering hot in the sun in the summer time.
They should have just stayed with good ol’ galvanized steel, wood and concrete for play ground equipment.