Sometimes it's easier to just say "enough" and toss it all. Picking through it to figure out what's donatable means having to think about each item, and by the time you're done you might decide you still "want" most of it.
People run businesses doing this, generally after someone dies.
It's a very poor use of resources to just throw everything into landfill.
Because of how our society is structured, this harder than it should be.