Why not allow the option to book by actual weight.
Bureaucratic inertia. Everything goes by the book.
I’ve been boating for more than 60 years. I’ve always kept a packet of emergency flares on board, because the Coast Guard requires it. I’ve never used them, and I don’t know anyone who ever used them. I would imagine that they are more of a danger than a help, since I’ve known kids to sometimes get hold of them and treat them like fireworks.
But I’ve religiously kept them on board, because I don’t want to be fined or deprived of the right to drive a boat.