Every man, at some point, will need to make his family's ends meet. Cauz here there is no grey income for most of people.
Income, spending the two ends have to be balanced for every family man, no matter how rich.
When students buying used furniture, they are trying to have their ends meet.
When someone bought a used Canon 5D, a used private JET, all have the same law/story.
ah... you buy everything new? good, that's likely that you are not bounded by this law of humanity.
but...that won't be (last) long. The guy won the lottery lost all his fortune in 14 years. That's the result of defying this law.