There's a whole lot of single-engine military jets, so I guess you're not interested in those?

@TooTea Indeed. I am less interested in military ones. I'll update the question.

Your question is based on a false premise @AleksG, turboprops are jets, and there are many single engine turboprops.

What do you do when the air carrier aircraft single turbine fails and you're a glider.

The Gimli glider had 2 engines; the engines didn't fail per se, they ran out of fuel due to human error in loading the fuel and flying with inoperative fuel indicator

@Gaston: The point is what do you do when you have no engine, which for a single engine aircraft happens after the first failure. For sure airlines are not happy with landing off the destination airport.

I think that if there was a sufficient market for a single-engine civilian jet there would be more than the Cirrus SF50 available for purchase. Obviously, the market for this type of aircraft is limited.

@mins OP did not ask about airliners, but about civil aircraft in general. A non-working jet engine is as useless as a non-working piston engine

@DeepSpace: No they didn't, but for small GA aircraft, emergency landing in a field doesn't lead to the same trouble, and is not the same concern for safety. Similarly overflying Paris (P23) at low altitude in helicopter (e.g. ambulances to hospitals) also requires a twin turbine, just for safety in case of first engine failure.

@GdD, "turboprops are jets" Then why do we use different words for them?

@Michael Hall - in the old days the term "rocket jet" was popular since rockets use jet propulsion (that's where JPL got it's name). As do turbojets and turbofans, which eventually sort of hijacked the name. Turboprops (mostly) do not use jet propulsion however since they use similar turbine engines they sometimes get the jet powered moniker, helicopters as well, i.e. the Bell Jet Ranger. But most people seem to use jet to refer to turbojet or turbofan aircraft.

@StevePemberton, "they sometimes get the jet powered moniker." Only in internet arguments. Most people call turboprops... turboprops. If the OP wanted to include them I trust they would have used this word for clarity.

@MichaelHall - I think it's mainly because turboprops use jet engines, of course technically turbine engines. But jet engines is a very common name including for turboprops, I don't normally hear the term turboprop engine. I agree the OP likely meant turbofan (they later specified civilian) as turboprops are rarely referred to as jet aircraft, although they did also use the term jet powered but the context seemed clear.

@StevePemberton, you seem to be contradicting yourself. Do you not normally hear the term turboprop, or are they rarely referred to as jet aircraft?

PS yes, turbine engine is a better word. Jet describes the means of propulsion, not the engine itself.

@MichaelHall - what I was referring to is that turboprops are sometimes referred to as having jet engines, thus it's not that non sequitur to refer to them as being jet powered. Although I don't think most people would phrase it that way, they would normally either say that it is turbine powered, or that it has turbine engines, or that it has jet engines. But like I said I agree that the context was pretty clearly set with the use of the term jet aircraft, which almost universally will be interpreted as meaning turbojet or turbofan aircraft.

I didn't get any sense that the OP is confused about this, and I think GdD's comment is unfounded. Please let's just leave it at that...

There is also at least one eprerimental single jet SubSonex - sonexaircraft.com/subsonex