It's almost as if they are the quintessential airplanes. Not in terms of performance, but like, if you want to show aliens how to make fixed-wing, heavier-than-air aircraft and you want to give them a "reference implementation" that illustrates the basic principles, you give them a Cessna 172/182. Easy to fly and to maintain, comprehensible by a technician without the specialized knowledge demanded by high-performance jets and stuff.