Jet aircraft (especially large transports) are often equipped with thrust reversers. Not a requirement for landing, but takes some of the load and wear off the wheel brakes and tires. They have them because of the high landing speeds and large masses they have to bring to a stop in a limited amount of space.
Propeller aircraft don't fly as fast, so landing speeds are not as high; for the most part, braking requirements are easily met with wheel brakes.
Even if reverse thrust was beneficial, reversing the engine's rotation would be totally infeasible; engines are simply not designed to run either way round, and any system which would decouple the engine from the propeller (as would be needed if you wanted to implement a "reverse gear") would be a safety/reliability nightmare, not to mention heavy and expensive.
Engines are a significant part of the total weight and cost of an airplane. Carrying around an extra just for reverse thrust would be impractical for cost/weight reasons.
Many propeller-driven aircraft are equipped with variable-pitch propellers, including many light aircraft; in theory, any of them could have a "reverse" setting, but (as described in one of the other answers) you would only see it on larger aircraft designed for operation on short runways.