When you are young and inexperienced, you don't know the difficulty of a subject. So as long as each step you take to advance your skill is achievable, and the feedback loop is good enough, you'll keep going. But as soon as you realize that you've only scratched maybe 1% of what is needed for mastery (when prior to that realization you felt like you were 90% there), it can be difficult to keep going.

As you get older and more experienced you get exposed to many things that appear to be "easy" but you then find out how much work it is (after you've sunk a bunch of time and effort into it). After enough of this exposure you realize that any skill that isn't realized by a majority of the population takes an immense amount of dedication and opportunity cost. So after a while you tend to stick with what you already know (sunk cost).

Of course your life satisfaction can improve with more skills you have, especially if they are skills that don't become too obsolete. For example being able to do some maintenance on your car (brake job, oil change, tire rotations, radiator flush...) can save money at a mechanic. And being able to take apart a sewer trap under a sink to clean out the hair clog is better than pouring a strong alkaline solution down the drain and hoping it works.

So it is really important to learn enough life skills while you are young to help build up a health and satisfying life later.