Problem is as stated above. As reliable as a Single engine turboprop is, it still doesnt have much system redundandcy; one Generator, vacum, fuel pump etc and these are much more likely to fail than an engine. In over 500 hours of KingAir flying and about 100 in light twins (not much I know) I never once suffered any form of power failure, but most certainly had regular Generator faults, instrument failures, pressurisation problems and one cockpit fire at night. Some of those would have been much more serious had we been in a single engine aircraft, especially over the Alps at night!