There is more to know in life than I will have time to learn. I memorize things I need often, or things I don't need often but in an emergency I will need to know them instantly - everything else I look up on need. It gives me more time to work on the things that are important to me. Unless your goal is to win a trivia contest you shouldn't memorize everything. (nothing wrong with winning a trivia contest if that is your goal, but only a few people can do it across all contests). Every one of your examples are things that I'd look up if I need to - in every context where I'd need them I'd already be using a calculator that has those built in.
Everybody should learn CPR, hopefully taking a day every year for the class turns out to be a waste of time at the end of your life but I still encourage everybody to do it. Some people need to know what e is - but it turns out I haven't needed that since I got out of school (learning to use e was in general good for learning rigorous thinking, but no need to memorize e as that value was someplace in my notes when I needed it). There are obscure things I use all the time I have memorized - but they are specific to my job or hobbies.
Looking stuff up isn’t free, which means it both costs time and frequently doesn’t happen.
Dismissing stuff as trivia doesn’t make that fundamental tradeoff go away. Do you need to know what 7 x 8 is, or the leader of China? No, but the cost of learning commonly used facts is far less than the non existent benefits of ignorance.
The key is commonly used. I don't think I have ever needed the square root of 3 in a context where I wasn't using a calculator anyway, so memorizing it would have been far more effort than looking it up (since any calculator can look this up instantly). Does it matter who the leader of China is - for some people it does, for other it is trivia not worth the bother of looking up. Back when I was getting my degree 7x8 was important to know (even if a calculator was allowed doing the math mentally was a trick I learned - most college calculus problems are selected to have easy math so if the math is hard I probably need to back up a step and fix my mistake - this trick didn't apply to other classes though), now it is mostly useful in context of proving to my 4th grader that I can do her level of math (7x8 might come up in real life, but only in contexts of a much harder problem so I'd be using a calculator anyway)
For me, the identity of the leader of China is genuinely as commonly used a fact as the lb-kg conversion rate, or that the circumference of the earth is almost exactly 4/30ths of a light-second.
Everybody should learn CPR, hopefully taking a day every year for the class turns out to be a waste of time at the end of your life but I still encourage everybody to do it. Some people need to know what e is - but it turns out I haven't needed that since I got out of school (learning to use e was in general good for learning rigorous thinking, but no need to memorize e as that value was someplace in my notes when I needed it). There are obscure things I use all the time I have memorized - but they are specific to my job or hobbies.