Plenty. They're far simpler to fly than multi-engine planes, but they don't have the redundancy or power needed for e.g. airliner purposes. For example FedEx operates a fleet of over 200 single engine turboprops (Cessna 208). Pilatus built about 2,000 PC-12s in the 35 years since it was introduced.

If we’re talking General Aviation, lot more than single engined military planes that is for sure!