People who spend their days emptying other people's overstuffed homes nearly all end up buying less themselves. Seeing the emotional burden that piled-up possessions leave on owners and their heirs changes their habits, so they give experiences like restaurant meals and trips instead of objects.
The things we treasure are usually worth nothing to anyone else. So most donated belongings never find a second owner and go straight to landfill or the incinerator. Expert sorters can tell at a glance which items have a buyer somewhere in the world, and too often the answer is that none does.
Makers can shorten a product's life on purpose or declare it unsafe after a set time, so that working items get thrown away and replaced. The book points to light bulb makers who agreed in 1926 to make bulbs fail sooner, and to car seats said to expire after six years with no evidence or government standard behind it. Electronics built to resist repair do the same job.
When new clothing and linens get so cheap you barely notice the cost, they are also made to last only a few washes. That floods the secondhand trade with more supply than anyone wants, and the goods are too flimsy to resell. Cheapness at the front end turns into an industry in decline at the back end.
The fix for the flood of unwanted stuff is to make things that last and can be repaired, so they still have value when the first owner is done. Where labor is cheap and repair skills survive, even goods rich countries scrap, like old TVs, get rebuilt from salvaged parts and sold again.