I bought a used car last year and the owner previous owner had oil changed every 5000 miles at the dealership per dealership recommendation, this guy had even the wipers replaced at the dealer. When I bought the car the oil was clean but every time you'd pull the dipstick there would be slime on it, I sent the oil for analysis to make sure the coolant wasnt getting in the oil hence suggesting the head gasket was bad. Analysis came back to be clean, I have had the car for a year now with oil changes at every 3000 miles, now every time you pull the dipstick out its clean as a whistle.
Sorry for the back story point being that oil is cheap, engines are not.
Maybe he didn't live too far from work & the motor didn't get fully warmed & driven enough to burnoff the moisture.