It might be for safety: having kids racing to get back to and from the family car while boaters are backing up, or otherwise engaged, has the potential to ruin an otherwise fun outing.
There is family parking right by the dock/peir & community building with the beach on both sides. You can park in the boat parking if there's plenty of open spaces, but it was designed like that for safety, ease of access to the boat launch & to highlight the community building, bathrooms & fishing pier. It does make sense if you think about the big picture & safety of the community (children). It is after all a multiuse facility.
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