It's just the nature of I/O design....
Fuel tank level above the engine so that any leak automatically siphons raw fuel into the bilge area.
Engine, batteries, and electrical systems all buried tightly under upholstery so fumes and heat can't easily escape.
It's a recipe for an explosion even when maintained in an OCD fashion. Straight inboard design which puts the engine midship is alot better/safer, but I/O boats blow up around here on a daily basis. They are, in my opinion, an engineering FAIL.