If you think about the last time you used cubits to measure something - viz., the last time you used your own body parts as a yardstick...

For me, it was about fitting furniture in a doorway. The most crucial time happened in a rental lot, where I had to measure a van by counting the number of times I could stand next to it with my arms outstretched plus one time with one arm akimbo: I had to see if some sculptures would fit inside.

In both cases it worked well enough, but if it had come down to a matter of inches I would have been sure to bring a tape measure.

Technically speaking, what you're talking about is rounding. Cubits are good for "close enough" measures; they didn't count fractional cubits.