Pat - There are a few things that have happened - as usual, not just one cause.
The American Furniture industry moved offshore to the delight of shareholders and owners. Owners got the financial rewards for selling or offshoring, and did not have to work anymore. No more pesky employees, just marketing ever cheaper product. The public loved it.
The resulting products that came back into the US were 1/3 the cost of their predecessors. When I started in 1990, there were some Henredon Mahogany tables that sold for 12,000 to 14,000 (1990 dollars). Once they went offshore and came back, they were about 5,000. This destroyed the craft makers of furniture since the competition was so cheap. They had to move up to 'art', or sell 'American Made', or go to something else (I went to architectural).
As for Unfinished Furniture, it used to be a market segment. Bottom feeder for sure, but shops in Tenn. or Ga could crank the stuff out, and it was priced right. Ikea killed them. Why would you go to the trouble of finishing it yourself when you could get it from Ikea in any of 2-5-8 finishes, no mess, and still cheaper!
No one ever went broke underestimating the intelligence of the American People was proved over and over again. We export first our jobs, and now our materials, all so we can pay less than $29.00 for a side table.