https://en.wikipedia.org/wiki/Natural_units https://en.wikipedia.org/wiki/Natural_units You can use units which are very neat and pretty logical for some thing

https://en.wikipedia.org/wiki/Natural_units https://en.wikipedia.org/wiki/Natural_units You can use units which are very neat and pretty logical for some things - and very inconvenient for others. That's, I think, the reason we have all that variety of units, which don't quite follow the same system. Centimeters are there just because of utility in less than strict cases; may be brains are simplifying by dropping unnecessary precision digits from consideration. Same for Kelvin - we don't measure temperature in, say, electron-volts, not only because Volt isn't a natural unit.