As I said in my edit, "because people are irrational animals who too often prioritize our current feelings over everything else."

Marginal improvements in quality which result in a marginal increase of cost/price often provide much better overall returns than just using a series of cheap substitutes that fail quickly. In some areas, this doesn't work, but I think shortsightedness is blocking truly better solutions in a great many cases. Particularly when true costs are being externalized.