The first reason was that they ended up costing twice as much to match the configurations (extra memory, the requisite software, etc).

The second and more critical reason was support. Apple just wasn't up to the task of handling a call from someone with somewhere between half a dozen and 100 macs at once.

The first reason has been changing in Apple's favor since, and the last time I checked around 4 months ago the cost was pretty much even.

The second I don't know, but one can hope.