The harmful aspect of such so-called “reusability” is that you are asked to submit on faith that whatever code you’re reusing, typically via function/API calls, does what it’s supposed to. From the viewpoint of purists, this act of unsubstantiated belief has no place in good programming.

You could even elevate such a discussion to encompass for e.g., what it means to live in a society where so many thingumajigs we take for granted are opaque devices sent down from heaven, as they were. It used to be that the average joe generally understood and could self-repair the gadgets he owned.

Well these days, “ownership” has taken a whole different meaning now, hasn’t it? Just like “reusability.”