Why should they? As long as they had a good run, what does it matter? Nothing lasts forever, certainly not any corporations. How many major corporations can you list which haven't either collapsed, been bought out, or significantly contracted in over 50 years? I can't think of any. Even IBM had a major contraction back in the 90s. Ford certainly contracted a lot, but these days they're doing great.
As for "durable goods", cars don't last that long. Sure, a few weirdos keep the 25+-year-old models in pristine shape, and other cheapos keep old cars running (barely) long past their prime, but most cars are not kept more than 2 decades or so. And this span of time is quite a bit greater than it used to be: 30-50 years ago, a car was considered junk when it had 50,000 miles on it. It's only been the last 10-20 years where it became normal for cars to go well over 100k miles.