[WJW]

It can also just be enjoyable and therefore not wasted time.

That said, the learned skills are only actually valuable if you can use what you learned later on in life. I've done my fair share of fiddling around with raspberry pis and kernel compiling when I was younger, but can't think of a single time in the last few years where I had to use that knowledge in my day job now that everything is containers+k8s+<some cloud hoster>. Maybe we can argue that it gave me a slight speedup when trying to grok the container execution model or something like that, but I could have gained that knowledge much more efficiently in other ways.