Very true of hot-water heaters, too. We had the misfortune of recently needing to replace the "original" one that came with our house when we bought in in 1997. The installer told us that all current models, including some quite expensive ones, are warranted to last seven years and might give us a few more. "But you won't get 25 years out of anything today."

Thinner vessels seem to be the main culprit. That does save a few dollars on materials costs.