Agree, I'm sure that the stats would fully back you up on that. Even the people that achieve their first goals, how many still go on to become competent, or abandon the idea, because it's too hard? I agree with you that people don't do hard things, or at least don't commit and stick to them.
But =)
I still think people should try if it tickles their interest. Because some people succeed. My theory is try 10 things and fail at 9 of them. IMHO the failures were worthwhile in search of the 1 success. And you have to learn something from 9 failures, right? But, I recognise, this is just my opinion. I'm sure a lot of people would not be happy with a 9:1 ratio.