in an interview from 1990 Alan Kay says that all the things he's carrying are to provide a "balanced day" so he can still practice music and play, even when flying somewhere for work
balance in life seems to be very important (unless you're fixating on being the greatest at a single thing)
using multiple parts of the brain during the day - to allow the parts "used" in one activity to recover while using other "parts" - this is the same idea with Westside training where variations of the main lifts are used to "work around" fatigue of the main lift