I thought Stanley cups is a weird choice to make "more shit" sound wasteful or a bad thing. Typically I think the American lifestyle is people carrying fewer things usually. I walk or cycle most places but always take a backpack, but I've frequently seen American-centric communities dismiss this as weird (because the car becomes their backpack).
As plans develop during a day it's easy to end up being out of the house 12+ hours, so it's comfortable to have a refillable water bottle, warmer layers, sunglasses, hat, umbrella, any other comfort things etc.