FWIW, I read a lot and while I often find it difficult to "recall on demand" particular things I've read, I have often experienced that I'll recall what I read in a relevant situation. I first experienced this when I did engineering calculus in college which covered a lot of (for me) obscure parts of calculus. And frankly I couldn't recall much of it at all, but when I took electromagnetic field theory and needed it to answer a question, it would bubble up to the surface.

That experience lead me to keep reading interesting things even if I couldn't recall them a week later on the assumption that when the need arose, if it was relevant, my brain might somehow surface the information for me.

That is indeed a perfectly valid trade-off, and not one the grandparent was mentioning. One thing worth mentioning is that if you don't read those books, you will probably not get a job that involves reading those books, nor will you turn your job into something that involves reading those books and applying their content.

If you are a software engineer, you can pretty much use linear algebra, calculus, algorithms in your dayjob, right there! Even if you write CRUD apps or the xth tower defense on android. It's all bytes and numbers and numbers stored in bytes and asymptotic behaviour and relational algebra and type systems and transistors, it just depends on how deep you want to look.

I'm currently a stay-at-home twin dad, and I absolutely crave to learn something new in my spare time (which varies from none to even two hours a day if I'm lucky). I don't care if I forget, but for me life just becomes too stressful without constant learning.

Of course, if I was working, I'd probably have enough to learn at work.

There is a good video from Niel deGrasse Tyson talking about learning.

https://m.youtube.com/watch?v=utedyJ7QRBs

His argument is learning is never a waste of time, even if you don't ever use and forget everything you studied. The simple act of learning is beneficial, it helps build connections in your brain. You develop skills that can be applied to other problems.

Baseball players waste 9 of every 10 swings on misses. It's a terrible waste.

So what you meant to say was with your current situation it is useless to you.