One thousandths of an inch?

How do you as a digitizer follow a client's direction to provide a design 2.875 inches wide? What makes a client even have a number of 2.875? We get this every single day.. but I am not sure how these numbers happen? Maybe because we are not metric like our digitizing software? Maybe because all end users are engineers and deal with numbers this small?

2.875 might as well be a solid 3 in thread.. by the time it pulls in on the sides.. and from 3 to 6 feet away for "personal space" reasons... really? heck after you wash the item the size will change.

So what is the reason so many distributors and embroiderers go to the thousandths of an inch?

not being snarky, really... just wanting to understand.. please help.