Some of the reason is indeed due to fuckery such as companies intentionally making things difficult or illegal to repair, however part of it is also due to economic reasons. If you’re trying to assemble something in the most economical way possible, you’re probably not going to go out of your way to also make it more repairable. You’re going to use single-use fasteners like rivets, glue, tack-welds, etc. - all things that are cheap to assemble the first time, but at the expense of more difficult disassembly later on.

In addition, diagnosing problems may be expensive depending on the appliance or machine. Would you spend four hours of your time repairing a dishwasher that could be replaced for $300? For some people it may be worth it; for some, not. I personally will spend quite a bit of time trying to repair something rather than replace it, however that’s more of an ideological choice rather than an economic one.

You’re going to need a lot of uncooked ramen, but it is possible.