It actually ties back to US Coast Guard and maritime law. For the last 100 years or so it was determined that boats had the right-of-way because they existed first, plus it can take a literal mile to stop a full sized tanker.
However, we recently had a meeting with one of the USCG district commanders and this rule is in the process of changing, largely because of the reasons you mentioned.
We do have black out time for testing/maintenance openings during rush hour, but boats can still technically request an opening during rush hour. It's a pain for us too.