I always try to get my non-DG friends to go disc golfing with me and they say it sounds boring. One day i proposed geocaching though and they all got hooked. For a few weeks we would always go geocaching, with a group of like 5 of us. Yet somehow they won't try disc golf? Like Naldoxcore said, it's fun the first time but after that, meh.
Have you tried showing them any of the Disc Golf videos on YouTube? That is what I do before I take someone out to play, so they know what it is