I doubt their reasons but not necessarily their conclusions. Breaking in to the laptop market seems fiendishly hard, at least due to economies of scale. Sure, 10% might be willing to buy a Linux laptop, but at what markup? When do you just say sod it and buy a Windows laptop to re-install. And from what I gather, Windows is so highly subsidized for OEM vendors that the cost is really negligible.

Further, it seems like the 10% savvy enough to want Linux won't be a perfect subset of the people buying laptops from brick and mortar retailers any way. Breaking in to the market would require a lot of other stuff, not necessarily retail (e.g. an efficient supply chain, direct sales to corporate, quality laptop builds, ...).