In short, "necessity is a helluva thing." It is not a technical explanation, but there is a great amount of truth in saying they were that way because they had to be to make it work.

Coming from another angle, the developers at that time considered those resources to be an amazing amount of plenty. Compared to, say, an 8086 with 128k or 256k of RAM, no HDD and maybe 512k or 1.44MB of floppy storage, those specs were huge.

If you're looking for other kinds minimal examples, I recommend glancing through the demoscene (https://en.wikipedia.org/wiki/Demoscene) stuff. To some degree, the "thing" there was amazing graphical outputs for minimal size.