I didn't explain my point very well. What I was trying to say was how can "laptop manufacturers that refuse to offer the 16GB RAM upgrade option" (as izacus put

I didn't explain my point very well. What I was trying to say was how can "laptop manufacturers that refuse to offer the 16GB RAM upgrade option" (as izacus put it) be considered market segmentation (as AceJohnny2 said in his reply to izacus). It's not a segment to those that don't sell anything to them, and because they don't sell to them, they have no (first-hand) data on how big that segment might be if they were to sell to it.