I've read a lot of interesting and borderline woo-woo reasons (hey, when your PhD work is in hypnotherapy, you run into tons of woo-woo!). Some were based on science like how plants (or animals) react to the same music played based on A equal to 432 vs. 440 and others referring to how everything is in vibration and, therefore, some things are more harmonic using 432 for A. That said, any equal temperament scale is going to have issues with some parts. I do find the whole area interesting.