I didn't say Europe does it, I said Europeans can't donate blood in America (because of a risk of mad cow disease). I don't know what Europe does with donated blood.

On second look, it appears that they only take samples of the blood and perform batch testing, so not too much of the blood is wasted if there is someone with a blood-borne disease in the pool. However, the point of this all is that tests for various diseases are incredibly expensive, and they perform batch testing to reduce the costs by using fewer tests. 8 million people donated blood last year and a single HIV test is about $50. That adds up. If someone in the batch has a disease, then they go back and test each sample individually. These costs can become massive, so they eliminate high-risk groups to save money on tests.