Well, just think “How would I do this cheaply and get away with it” for a good enough “Engineering” approach for this case.

The really expert “Engineering” stuff related to things like maintenability, reliability, robustness and so on (which I myself am not qualified to talk about, as even though I have an EE degree, that’s not actually the domain of Engineering I ended up working in), isn’t, IMHO, really necessary to understand to explain why those designing circuits commercially would chose the commonly available and cheaper components if they can.