Combining your two comments, I know Pi to ten decimal points because it was something I learnt at school and I doubt I will ever unlearn it. Some people use a nmemonic such as "How I wish I could recollect Pi easily today".
(I wish I could always remember how to spell "nmemonic").
However I find 3.14 is usually close enough on most occasions. Like you, I see little point knowing more decimals for Pi.
I can name the 50 states of America because I once made an effort to do this and again I am not likely to unlearn them. Not much use unless you also know where they are, how big they are, rivers, cities and so on.
Occasionally I try to learn the elements of the periodic table. Not so good. Not much use unless you learn something about them. For example in one part of the table the sequence is not toxic, very toxic, very very toxic, extremely toxic, not toxic, toxic, and toxic.