My understanding of the 'not if you've ever done steroids' problem is regarding the use of needles. They just don't trust us not to have shared.

As for the benefits of giving . . . we males need to get rid of a build up of toxic iron in our blood. Females do that on a monthly basis, whereas we men don't have that option.

Lowering our red blood cell count is another useful benefit.

Also, as far as I am concerned, if someone will die without receiving a blood transfusion then I doubt a touch of man made testosterone is going to kill them. I'm fairly confident that if exogenous testosterone would be that dangerous we would be told in greater detail why not to donate and they would also test for this exogenous testosterone before giving to the blood to the patient.