I mostly work in Manhattan apartments in NYC. Because we Manhattanites have such a small real estate footprint, it is easy to excuse the clutter. We just don't have enough space! And then I go up to the Bronx or out to New Jersey or up to Connecticut -- where people have more reasonable square footage. I find the clutter problem to be the same -- whether people live in 500 sq ft or 1500 sq ft. The larger a home, the more people fill it up with stuff.
If people understood why they have a hard time letting go of clutter, they might then be more inclined to let go. Here is an interesting article on why we keep clutter and some suggestions on letting it go. http://tinyurl.com/l8calku