Question

3. Why is a cubit or footstep or used as a standard unit if length?

Answer 1

Answer:

Your question is unclear...is it-

"Why is a cubit or a footstep not used as a standard unit of length?" (I am considering it this way)

Well, a cubit or a footstep is not considered as a standard unit of length because each individual's hand and body lengths are not the same. Some may have longer hands, some may have shorter. A table might be 10 cubits for one person, while 15 cubits for someone else. To avoid confusion, the French had invented the International System of Units, agreed by many of the countries, known as the metric system.

Extra point: I wrote 'many' since not all follow the metric system. USA has it's own system of units known as the imperial system.

Hope this helps...