Sometimes it is because the product is processed on equipment that previously processed something containing gluten.
Sometimes it is processed on dedicated equipment but in the same facility that processes a gluten-containing product and dust in the air cross-contaminates.
Either way, when you eat such a product you know quite soon that it is not gluten free, and you never buy that product again.
Such processing is "penny-wise and pound foolish." Yeah it might save a bit in processing, but just lost another long-term customer.
Bad business decision.
