Only 5.3% of US welders are women. After years as a professor, I became one

Best guess is the tolerance required for the pipe length was tighter than you can reliably get going off of a tape measure foot (which are often loose, worn, bent, etc. and not a reliable starting/zero point for precision measurement).

OK thanks. I wonder if there are a lot of cases in which cutting and welding an 8 foot pipe requires the accuracy that that method doesn't provide.

Not many that I can think of but it would make sense if she were starting with 16' or 24' length of tube as then you would really want to measure the whole length and then mark where your cut or cuts would be as you may already be at the edge of the tolerance. For instance, if you have a 15'11.125" long tube and you need to make two 8' tubes with a tolerance of +/- 1/2 then you need to be dead on with the cut, even though the tolerance is big (which you'd expect it to be on a 8' tube).