People who code should know how to build a computer for themselves

Not necessarily in my opinion. You can very well be a techie or a programmer or w/e without knowing how to put together your own desktop. I know it is not that hard with a little bit of research but still it is not a requirement in my honest opinion (depending on the sector maybe, such as in web development). It is however true that most of those who are developers consequently like tinkering with stuff like that

@liammartens I usually tinker with building more than programming

I am someone that can code and can build a computer. However I must disagree with you here completely.

People who eat should know how to slaughter a cow XD

Building a computer is helpful and interesting but not mandatory imo

People who drive a car should know how to build one for themselves.

I would suggest that it's more important to understand the architecture than know how to build a computer. Knowing where the maximum values of integers etc come from is quite important. Knowing how to plug in a hard disk isn't so.

I do feel however a rounded knowledge is important. Using @futureexcon 's analogy you shouldn't have to know how to build a car but knowing how to maintain it ( check the oil, coolant etc) and why you have gears is quintessentially important.

Why? Does this mean I shouldn't drive / microwave stuff / use my phone any more?

@biscuit it doesn't at all! I just find not having to rely on someone else for stuff is good! I guess I'm just independent and have a mindset of why should I get someone else to do this for me when I can do it myself. I guess I've suggested everyone should be of a similar mindset to me without actually realising.

Some people are just happy getting the "correct person" to do it. I like to know that a job is right.

Ehh kinda disagree bit hard building ya own Mac lmao

Following you're reasoning, we should also know how to build a microprocessor, a hard drive disk, RAM and motherboard.
Building a computer is merely putting some legos bricks together paying attention to compatibility. It doesn't require much understanding of the system architecture.
Better know how a proc react to instructions rather than how to plug it in your motherboard when you actually wants to program it.
Does the developer really care about thermic paste? This is a completely different job.