Companies purchase many items (like towels) as a large single order from a manufacturer. They may order many 10s of thousands to get a competitive price, once that stock is gone, it's gone. To continue to supply the items would mean another large order, they would have to be certain of selling the item. Also when dyes etc are involved, colour matching another batch is a lottery (hence codes on wall paper etc). Have you noticed how often companies like Nikon, Canon etc update their cameras etc ?. They plan for a set production run and once that number has been sold they re-tool and update the product regardless of it's current popularity.
This is how we get many products at low prices, if you want continuity you may have to pay for the privilege and purchase high end branded products, even then I doubt the same product will be available in a years time.
We buy only white crockery now (someone keeps breaking them), but even then we can see mismatches in colour in apparently identical items.