When you buy a glass of wine at a nice restaurant, it doesn't come in a beer stein. If it did, the 4 ounces would be dwarfed by the glass and you'd feel like your host was ungenerous.
Closets, it seems, are always just a bit too small to hold our stuff, regardless of their size.
Busy corporate lawyers spend twelve hours a day at work, and somehow, are busy the entire time. It's easy to imagine that they could get their work done (most days) in 8 hours, but the container they're using is size XL, and so the work expands to fit.
Dieters have been shown to eat less when they use smaller plates.
Silicon Valley helps entrepreneurs feel that things are possible, but it also sucks the joy out of the process because so many people are keeping score on an infinite scoreboard.
Portion control via vessel size is a secret to success and happiness.