An Army report on testing Hololens indicates the testing didn't go well.
It made soldiers physically ill. On top of that, it had shortcomings which would potentially compromise the safety of the soldiers in the battlefield.
“The devices would have gotten us killed,” an Army reportedly claims.
arstechnica.com
Symptoms included nausea, headaches, strained eyes.
But even if it didn't make the soldier sick, the weight of the device limited the movement and the field of view, which are again potential liabilities in the battlefield.