Two units describe the same bar. A section is bought by weight and sold by the metre, and a system that cannot hold both produces stock figures that never reconcile with the yard.
Remnants accumulate quietly. A two-metre offcut is worth real money to the next customer who needs exactly that, and a yard that cannot find it buys a full length instead and loses twice.
Certificates belong to the batch. Mill certification has to follow the material to whoever ends up welding it into a structure, and reproducing it months later means knowing which batch a cut came from.
Cutting time is where quotes leak. Ten cuts and four holes is an hour of somebody's day, and pricing steel by weight while giving away the processing is the most common way a stockholder loses margin.