In some ways, the chairs could be perceived as symbol of hospitality. But, looked at another way, they communicate inactivity and complacency. Standing, even when still, looks like activity more so than sitting does to me. Perhaps when a customer enters a store such as this, and can sit down and use the equipment without interference or engagement with the staff, they become less motivated to do anything more than that. Why buy the laptop when you can have the surfing for free? Perhaps when they enter a similar store without chairs, and are engaged on a regular basis by friendly but determined staff, there is a sense to take some action, even if that action is to leave empty handed.
There are lots of chairs at Microsoft Stores, few at Apple Stores.