It's hard to comprehend how important and influential Prof. Kahans work on floating-point arithmetic was. The fruits of his work are now everywhere, touching almost everyone's life in one way or another, mostly going unnoticed.
We got through it, but this was not a very smooth innovation. 1 | 8 | 23 is a totally weird bit layout. On the other side, the importance of this to numerical and scientific computation was immense.
Maybe this is what the engineers of the time were thinking. Each digit uses 4 bits (nibble), but then we would not have a fixed number of digits and it would be harder to achieve what was possible with float and double, systems that used a fixed number of bits. I think the key idea that helped adoption was that in engineering they use significant digits anyway... After those digits they do do not care about precision.