Why can't Blood Elves have Shamans?

Blood Elves are not ones that attune themselves to the world in a harmonic sense.

There is not much leeway for a race to indulge in spiritual serenity when they are wracked with a severe addiction to the arcane. The Blood Elves do not soothe and coax power and magic from a natural setting, they tend to rip it forcefully from the environment, finding scientific methods to tap into magical currents.

Blood Elves have never been deeply invested in their environment as a mother. They treat the environment as a resource or a tool for further power.

That is why they aren't shaman.