http://www.forrester.com/go?docid=46545

A lot of the established enterprise server/PC vendors – e.g., Dell, HP, IBM, etc., may accept competition with Apple in the consumer marketplace as unavoidable, but given their high domination of the enterprise market, Apple wouldn’t benefit by being seen as actively trying to compete – yet. The slow/gradual penetration of enterprise customers via halo effects serves Apple well since they’re not dependent on enterprise revenue streams. They can afford to wait for their visibility to increase in enterprise customers to the point where staff and management start actively planning deployment of Apple solutions.

Thus, rather than having to actively engage in competition in what is quite a cut-throat market, Apple can have customers bat for them.

Steve Jobs said that Apple TV is a “hobby” for Apple; one could argue that enterprise involvement is sitting somewhere between “hobby” and “core business” for them – it’s at a good point where they don’t have to invest a lot of work for the sales they make, their customers do much of the selling, and there’s good money to be had by not having to enter into price-wars with competition.