It is how warranty works. The problem is there are so many things that the customer can mess up due to their own errors or negligence. Warranty doesn't cover normal wear parts or maintenance parts after the first scheduled service, which in some cases can be as low as 5 hours. As a lawn mower tech I deal with a brand of trimmers that carries a two year manufacturer warranty. And then when you look at the warranty in detail is specifically excludes normal wear parts. That list included spark plug after the initial service, air filter, fuel filter, starter handle, starter rope, starter pulley, starter spring, inner spool, outer spool, bump head, bump knob, and string reel. Then you start asking what they do cover.
I bet if somebody actually dug into the details there is probably a list of things that are excluded from the warranty on automobiles, Contaminated fuel is one example. Or putting gas in a diesel engine, or diesel in a gas engine. Fuel system warranty goes out the window, and in the case of gas in the diesel, possibly the engine warranty goes by-by also.
On average only 1% of all failures are due to failures in manufacturing or workmanship.