Everything is guaranteed to fail eventually. At no point in the process of designing something does an engineer or manager decide whether to make something that's going to fail or something that's going to last. You make something that you know will fail after n years. n depends on how much you are willing to spend on the most failure-prone parts. What's a reasonable value of n? Well, it depends on a lot of things, doesn't it?
You say that spending less on parts you know will fail is malicious, but everything fails eventually. If you know that your resistors are likely to last 100 years, and your capacitors (even the best ones) are like to last 20 years, is it malicious to not spring for the resistors that will last 200 years? You have to make practical decisions about the level of quality that you're aiming for at some point.
I know that planned obsolescence is a thing, and it should be illegal (in certain forms). How common is it? I don't know. Do you? Maybe I should have said "it's not necessarily malicious", because it's not. You can make a cheap product just because you think there's a market for a cheaper version of a good product. Does that mean you want the thing you're making to fail? Not necessarily. Maybe you just want to serve a market that wants a cheaper version of something. I sometimes find myself wanting to buy the cheapest version of something because I only need it for a brief period of time. Is this wasteful? Sometimes. Should it be illegal for a company to sell me a cheap version of a thing? Maybe for environmental reasons, but not for consumer protection reasons.