Does anyone remember how Macs were sold before the Apple store? You had the mom and pop stores that had the expertise but not the volume to make an impact. You had the online stores that had the volume but if you weren't looking, specifically, for a Mac you wouldn't know there was an alternative. And then you had the B&M stores like Sears, CompUSA, etc. They had Macs, tucked away between the radar detectors and vacuum cleaners. Even if you knew you wanted a Mac the sales staff would try to pass you on a Windows PC. With "friends" like these who needed enemies.
Jobs knew he needed to switch things up so worked on retail store concept. Put it in a place with a lot of foot traffic (mall, downtown store, etc.) and make it easy. Want to check email, facebook, etc? Everyone knows you do it at the Apple store, Starbucks wifi costs money. Now you've got everyone in your store using your OS. They might not buy it right away but you've planted the bug in their ear.
For retailers it's just business. No one demands a Linux laptop and the few that due aren't a large enough market to keep them in stock and on the sales floor. If desktop Linux wants to have an impact it's going to need a lot more than a website with ISOs.