You're not alone. I listened to a podcast a while back on this subject, and the reason that the blood "market" runs solely and strictly on donations it's because earlier in history, when the medical establishment paid for blood, they were only able to get skid row types to contribute, and needless to say, the quality of the blood wasn't good.

http://freakonomics.com/2013/06/05/is-paying-for-blood-a-goo...