Like painking said, it's mostly for roleplaying purposes right now. Before I land kerbals on a new planet, I like to go through the stages of sending a probe to survey for a landing site -> sending a rover to check out the site at ground level -> finally landing the kerbals. I know the kerbals are expendable, but I'd still like to reduce "risks" It also requires less fuel to maneuver a probe into different orbits in the same mission to get different views than maneuvering, say, a pod or even a rover.