I had more than once, back when I first installed Debian in the late 1900s and early 2000s, and I believe my experience wasn't unique.

Back then, not requiring any loadable firmware was common; the hardware either didn't require firmware, or came with the full firmware in a ROM chip in the device itself. And that explains the issue: Debian is an old distribution, coming from these times when not having non-free firmware (or even any firmware at all) in the distribution was viable, and often fully usable.