Learning new skills is fun. But the problem with most of the skills you can learn quickly is that there is only rare opportunities to use them. By the time you finally have a chance to use one you have probably already forgotten the whole thing.
Or maybe that chance never comes. There are skills that would be nice i wouldn't ever need to use. Like some survival skills for the worst case scenarios. Is it worth learning those if they are not supposed to ever become needed. And if they do, will I remember them anymore when needed.
Practising regularly all those skills would be one solution. But that would greatly reduce the amount of skills I could accumulate. There is just no time for them all.
But it's not always necessary to remember all those skills. Especially the less useful ones. Maybe someday the opportunity comes and I happen to remember it correctly. With more skills, even most of them forgotten that still gives a better chance to get to use one compared to knowing just few skills really good.
And in the end, it's not just learning any particular skill. It's about broadening you knowledge. There is definitely something that'll stick.