I think you'll find that even the folks with diesels have gas on board for their dingy. And being "diesel powered", there's a temptation to get a bit lax about the storage of the gasoline.
Our boat is Atomic 4 powered, and one of the first purchases was a Zintex fume sniffer. In 23 years, it's gone off twice. First was a gas jug for the outboard that had gotten onto it's side in the lazarette. Second was a bad gas tank fill hose. No problems related to the engine itself.
Another plus to the Atomic 4 is that it's lower than a comparable diesel as the valves are in the block. The diesels have overhead valves, making the engine higher. Putting a diesel in my boat would mean losing some seating at the fwd end of the dinette table.