I teach a lot of adults as well, and I find that a lot of it comes down to the fact that most adults are used to being good at something. They've lived a while, perhaps are professionals and maybe in positions of authority in their field.

Then, they come to piano and they are starting all over again. You and I know that's not really the case, but it can have an impact on a person's ego. That, and unrealistic expectations of what it takes to learn to play a piece or a genre.

I like your approach to making sure that they are at least listening to the music and learning how to connect what they hear with either notes on the page or keys on the piano.