I worked in distribution for 21 years and worked close to the manufacturing process so I'll take a shot at it cause I don't think Cookshack will respond to your question.
They must have been selling more of the stainless steel. Eliminating one type cuts down on raw material inventory by not having to carry both housing materials or paint. Production doesn't have to be changed to handle another material, and the paint process can be eliminated. It makes it simpler and more efficient to manufacture product, maintain inventories and process orders.
The good part is by Cookshack becoming more efficient, it will save us all money in the long run.