Time is money in manufacturing and assembly lines are not set up for "extra work". More efficient to either scrap or sell off-spec products as "blems/seconds" versus paying for sort, clean, repack.
In a paper mill, giant machines make giant rolls of paper that is converted into all sorts of packaging, tissue, etc. When they change grades of paper the machines do not stop and the "transitional" paper that is not the original grade or the next grade is "blem" and either sold at discount or recycled.
I managed a soft drink carton plant that made millions of soft drink cartons per day - when we switched from "red brand" cartons to "blue brand cartons" on the run at speed we had "blem" cartons that were fully functional but not the right color until the machine settled on the new ink.
In a paper mill, giant machines make giant rolls of paper that is converted into all sorts of packaging, tissue, etc. When they change grades of paper the machines do not stop and the "transitional" paper that is not the original grade or the next grade is "blem" and either sold at discount or recycled.
I managed a soft drink carton plant that made millions of soft drink cartons per day - when we switched from "red brand" cartons to "blue brand cartons" on the run at speed we had "blem" cartons that were fully functional but not the right color until the machine settled on the new ink.