Design life.
The caps are fine, for what they are. Give or take occasional formulation mistakes, but that's happened even to large brands. This particular brand makes as wide a range of products as anyone else; all of which will do more-or-less what the datasheet says. If the type chosen isn't well suited to the application, or a longer lifetime is desired (a desire you are asserting, not the manufacturer!), you get unexpected failures.
Key word, "unexpected". The manufacturer is happy with calculated lifetime, and their customers are happy enough at the price point. Assuming, you know, a fair market and stable equilibrium and all. Which... sometimes.
Also assuming that it's past EOL. You didn't give a mfg date, which would probably give it away (if it's labeled at all, anyway).
Tim