Have you ever had a plumber, HVAC tech, electrician, etc. come out to your house for something, and had them explain it to you? Have you had the unfortunate experience of that happening more than once (with separate people)? If so, you should know why this matters: because if you don’t understand the fundamentals, you can’t possibly understand the entire system.
It’s the same reason why the U.S. Navy Nuclear program still teaches Electronics Technicians incredibly low-level things like bus arbitration on a 386 (before that, it was the 68000). Not because they expect most to need to use that information (though if necessary, they carry everything down to logic analyzers), but because if you don’t understand the fundamentals, you cannot understand the abstractions. Actually, the CPU is an abstraction, I misspoke: they start by learning electron flow, then moving into PN junctions, then transistors, then digital logic, and then and only then do they finally learn how all of those can be put together to accomplish work.
Incidentally, former Navy Nukes were on the initial Google SRE team. If you read the book [0], especially Chapter 12, you’ll get an inkling about why this depth of knowledge matters.
Do most people need to understand how their NIC turns data into electrical signals? No, of course not. But occasionally, some weird bug emerges where that knowledge very much matters. At some point, most people will encounter a bug that they are incapable of reasoning about, because they do not possess the requisite knowledge to do so. When that happens, it should be a humbling experience, and ideally, you endeavor to learn more about the thing you are stuck on.