I mean, how do you know your webserver doesn't have a bug? How do you know your OS doesn't? Just write those yourself? How do you know yours doesn't? One must still verify the key functionality regardless.
But, you're not wrong, some people reach for every library and framework they can, and others focus on building the most minimal and understandable thing that will work. I'm not saying writing your own server in assembly, but, avoid unnecessary junk and magic and libraries.
It's the classic dilemma: in this world of ours, one can either return to monke or progress to crab.