First of all it's largely not actual sand (silicon dioxide) like you get naturally in most of the places like up in Daytona, where they ran the stock-car endurance race on the beach for years before a paved track was built.
Nope, common road vehicles have never been ideal way down on South Florida beaches, even back when there were no rules. The ATV's like the lifeguards have are the kind of thing that really works, or a dune buggy with the fat tires even in places where there were no dunes. Anything heavy just sinks more than you would want.
Because the beach there is so soft you can feel the difference as you walk, and it consists more so of particles of eroded seashells (calcium carbonate) having much larger size, much more random and irregular shapes, and a much wider particle size distribution than the far more universal and familiar true sand elsewhere.
And it all leads more steeply into the Atlantic Ocean, it's not the really wide sandy beach that sometimes is considered more desirable.
Notwithstanding any replenishment which can can upset the balance for a period compared to naturally deposited or eroded material.
The sandcastles that can be built have differences in limitations that can be felt by hand.
And IIRC the building contrators were not all of the highest integrity.
I would say my experiences exploring many of the hi-rises in nearby Broward as a teenager after-hours at the construction sites as they were being built in the late '60s & early '70s was not unique.
All kinds of kids did this in South Florida . . .
There just weren't that many kids when the bulk of the population is retired from up north.
I'm sure I could come up with a word or 2,000 on the subject or even more now after the deadly collapse.