On the opposite, i'm not surprised at all. The desktop market share worldwide is less than 10%, and about 10% of all US computers. Apple is still a small company. It probably always well be too.
At least in the terms of traditional computers, then yeah, Apple are unlikely to gain much marketshare, despite it constantly rising due to the popularity of their iDevices.
In the mobile world however, Apple has the minerals to be top dog. The only problem preventing more people from buying their products I feel is the price. In this current economic climate, people are opting for cheaper Android phones which in all honesty, work just as well.