Keep in mind that most of the powerboats are traveling a lot faster than 15 knots. My son's boat cruises at 30 knots and is capable of going much faster. Therefore, skipping across the bay at 30 knots and not lighting up what is around you once in a while is akin to driving down I-95 at 70 MPH in the middle of the night with no headlights on. If you were driving down I-95 at 5 MPH with no headlights on it would be a piece of cake - but at 70 you would be in deep $hit if the guy in front of you had no visible lights.
Secondly, 99.9 percent of the boaters I've encountered in the past 6 decades couldn't tell you how far away a boat is while traveling at night. The perception of distance in pitch, black darkness, even when seeing a boat with full running lights, is out the window. So, just because this guy lit yo up doesn't mean he's doing something to piss you off - he's just trying to get home safely without running into a very slow moving sailboat.
Many years ago, Sea Ray used to have a headlight option for their boats. I know of a couple charter captains that had them installed and they were the best thing since sliced bread for weaving your way through unlighted day markers, unlighted buoys, avoiding pound nets, and weaving through the minefields of crab pots. They didn't leave the lights turned on, but instead, just flicked them on from time to time to light up the unseen objects in their area.
Think about it,