I guess it is more or less due to fear of reduced margin and control, not to say that the counterfeit/used/defective problem still stays. When they sell through local shopkeepers, they are actually selling it through channels, which gives them info and control over buyer and their choices, and a price they can decide. Now in case of online sales through 3rd party e commerce sites, the sellers listed on them can be authorised local shopkeepers which are trying to expand their reach, or some random person who procure laptops in bulk(via gray market) or at low cost by acting as a corporate buyer, and then sell those laptops at slightly higher prices ,a condition which will cause loss to the company, and may cause legal hassles for them(customers pursuing warranty claims against grey market goods). I guess it is completely fair on their side to warn others, but not fair to block warranty claims when the seller is an authorised person.