Imagine you were an architect of buildings. Your day to day job is to design mundane strip malls and gas stations. You have building code on your side for much of the process. As long as you don't violate the regulation, you at worst can only make an inconvenient building, but not a dangerous one.
But imagine instead that you're building a large office building every six months, your clients demand you don't reuse any design principles on your future clients, and you not only lacked the building code, but also 1/4th of the heavy machine equipment, 1/2ths of the tools, and 3/4ths of the raw materials. I don't just mean you don't have them in stock, I mean nobody has invented them yet. And of the ones that have been invented, we don't even know all of their material properties, say nothing about what material properties we should be looking for. Will this particular bolt we are using with these particular cross beams hold up to the stresses placed on them? The answer is unknown, and I'm some cases unknowable.
It's really easy as a user to say, "they should have tested this more". While strictly true that more testing may have found your issues ahead of time (presuming the right tests were done), it is inefficient engineering to exhaustively test things. Even mechanical engineering bases a lot on statistical modeling, which will always, always have corner cases that don't match reality.
In the real world, people had to learn the hard way about things like lightning rods and sacrificial electrodes. They didn't come about from "testing during development". They came about from testing live, and seeing which buildings and boats did or did not burn down or sink. That's not bad engineering. That's just the nature of unknown problems.