The reason this naming convention (omitting the number) works for Macs but not for iPhones and iPads is that iPhones and iPads come with a lot of accessories (c

The reason this naming convention (omitting the number) works for Macs but not for iPhones and iPads is that iPhones and iPads come with a lot of accessories (cases, car kits, etc) that need to be form-fitting. So, you want a case for iPad 1 and not a generic iPad case. You want a car kit that fits the iPhone 3GS and not a generic iPhone. For iMacs, you don't really need any accessories that care about the shape of the iMac, they only care what ports you have. For MacBooks, usually laptop cases just care about how big the laptop is (i.e. 13 vs 15 vs 17 inches), and don't have to be as form-fitting as iPad or iPhone cases. As a result, it's more important to know exactly which iPad or iPhone model you have, than it is to know exactly which iMac or MacBook model you have.