Have you been up there recently? The govmint spent a shite load (of taxpayer money!) on restoring the lighthouse cottages so they could be rented out. On the scale of things I doubt a few well-heeled tourists overnighting up there was going to detract from the place. If anything, it may have directed more funds into the park.
Last year the Barrenjoey Cragcare regulars were allowed a sleepover in the (refurbished!) lighthouse — fun times for all. Dave Noble got a nice shot looking back over the isthmus. The perks of volunteering.