Yeah, my explicit mention of kitchen scales and calipers was intentional, they both become much more useful if the user can choose to zero the readout at any time.

This is less true for a bathroom scale.

Went not just stand on it while it tares and ignore the negative when you step off?

All the digital bathroom scales that I've encountered refuse to display negative measurements.

Well my kitchen scale does. Though I don't know many people who weigh less than five pounds.