I remember shopping at Dillard's department store because it was one of the only department stores in my area that accepted Diners Club. Acceptance was a tiny fraction of even Discover or Amex acceptance.

It was also weirdly calibrated at the time: You earned 2 points per dollar, but redemptions required twice as many points. So back then $1000 spend earned 2000 points, but you needed 2000 points for 1000 miles. Now $1000 spend earns 1000 points, but you only need 1000 points for 1000 miles. So the "calibration" just made it weird, but had no material effect on redemption value.