I'm not a big Cub fan myself. I think they are popular because it's really easy to make something that looks like a Cub, and the flight characteristics make a tame trainer. As such just about everyone's first RC plane was some sort of Cub. They are a pretty realistic scale flyer, like Bricks says you actually need to use the rudder to make them track well and they fly well with a wimpy motor.
As a taildragger they steer easily with rudder on the ground, and don't need a smooth surface for a nosewheel to track on. You don't see many 172 RC trainers despite them being the most popular trainer in general aviation, probably because there would be a lot of smashed nose gear out there.