I’m a Level 2 CASI certified snowboard instructor. I taught hundreds of adult beginners over the years. I myself started as a never-ever when I was 35.
Season starting soon, come up (I’m at Vancouver/Grouse) it’s awesome!
Snow boarding is also done upright, so your spatial awareness is the same.
Try teaching adults with no gymnastics background how to handstand. Kids can pick this up in weeks. I know very few examples of adults managing it. And even then their skill level is not very high.
1) A fear of embarrassment while learning - because as an adult learner you're at the bottom of a far wider range of skill levels of people your own age than a child is when they're learning. When you've been working on your French for two years, and a five year-old French child speaks with a facility you don't have in your wildest dreams, well, remember that that five year-old has been working on their French for five years; and while they were learning, they never had to feel like they were too far behind every other under-five in the world.
2) The constant encouragement of adults to concentrate on improving the things that they're already good at, and not to waste too much time on the things they're not good at that aren't necessary for their jobs. I think part of this comes in the form of theories that it's impossible to learn things after you're the customary age for people to learn that thing. Or worse, that everybody who is good at a thing was anointed by god or genes to be good at it, therefore if you aren't good at it already you probably weren't chosen.