A similar point: I've never actually met someone who has 4 weeks of vacation to actually use all 4. Generally, when you work up to the point at a BigCo where you can command a larger vacation, it's hard to remove yourself from the day-to-day practices of work.

Plus, America has an embedded culture of trying to "outwork the competition" in everything we do, from sports, to academics, to the workplace.

It stems from the postwar era of growth where human hours logged in an office were the only drivers of progress. Obviously the world is different now, with the advent of the internet, but old habits die hard.