Old dog? New Tricks? What does it take to get an adult to take up a new hobby?

So, this is something i've been thinking about a lot, as an artist and a teacher.
I frequently hear people say "oh, I could never"... fill in the blank - do yoga, pilates, take up a martial art, knit, whatever.
And yet, I frequently meet people in my classes that are new to dance or pilates, and excited about taking up a new skill. Some of them stick with it; Some of them disappear after one class when they realize that you're frequently...not a master on your first day trying out a new thing.

Is that the thing that holds people back from trying something new? We dont like anything we're not good at?

I frequently think that it's a REALLY good thing I was forced to learn how to ski as a child (my dad's an upstate New Yorker). Had I not, I would NEVER have endured the cold, discomfort, and falling down that learning how to ski entails, as an adult.
But I dont live entirely within my comfort zone - I frequently take up new artistic hobbies or physical disciplines - I'll try any kind of physical class, or cooking class, or just some random junior college class that looks interesting - Am I just a class taking kind of person?
Is it a personality type? A stick-to-itiveness personality type or a quest-for-new -skills personality type? An inherently geeky personality type that just wants to know little bits about everything - or master as many seemingly impossible things as we can?

Are we paralyzed in the outdated notion that grownups just know everything - which means we cant show up to learn something as a beginner, because it would require admission of not-knowing?

Do we just stop prioritizing learning as we age?

This is an open ended question I dont really have an answer to, just something I've been thinking a lot about.

As we get older, do we become less open to the public humilation inherently involved in learning new skills? Do we grow in to a fear of being wrong/not knowing? Shouldn't we become more fearless as we get older, instead of less, in the face of all the things we've survived to become grown-ups?

-Cera