Mean time between mission failures for turbofan engines tends to be over 80,000 hours. Mean time between mission abort would be about half that, or 40,000 hours.
With two engines, mean time between mission abort would be 40,000 hours.
You simply fly a single engine aircraft differently. With a hiccup, you abort and fly back. With a two engine aircraft with a hiccup, you continue to fly, and monitor it. If you lose an engine, you fly back.
All bets are off if someone is slinging 37mm cannon fire at you. You are nearly as likely to lose both fighter engines from one hit as you are to lose one engine. That is because two engine fighters have the engines close to each other.
My thinking is, if you’re flying around somewhere in the Arctic Circle, hundreds of miles away from anyone or anything, and a turbofan engine developes a “hiccup”, I’d like to have another engine to get me somewhere else.
Same thing with Navy aircraft. Two hundred miles away from the boat, I’d like to have “another” engine.
I’m only talking about mechanical failure.