1. We have more people without much disposable income (which is composed of two populations: poor immigrants with few marketable skills, and two, poor Americans left behind due to shipping MFG overseas --going on for a while, jump-started by MFN status in the 90s).
2. People want cheap stuff. It's unfortunate. It means more disposable crap going into the landfill. Save up and buy something that will last. (unfortunately ads don't contribute to model behavior here)
3. Overseas there have always been these cheap goods stores (100-goods stores in East Asia (百貨公司)), we're just late to the party --however in Asia these popped up because people didn't initially have disposable income as their economies evolved after ours. They are on the upswing, we're on the down.