There is no school math test that will require you to know the digits of Pi, except as a silly extra credit question.
The fascination is just dick measuring. "I'm smarter than you", for memorizing a longer string? It's quite dumb, but American media loves to use the dumbest possible ways of demonstrating that a character is intelligent, because uh it's really really hard to demonstrate "This person is very intelligent" to a subset of the population that is mostly at a middle school reading level and barely comprehends basic arithmetic, let alone algebra.