Why is there ************** when people want to donate blood?

I have been wanting to donate blood whenever I see a donation setup in any shopping centre but have been turned away every time. I have been a blood donor since the age of 20, but am now considered to be "too old'. Just before the Easter weekend I saw an appeal for blood again, so having been turned down got an email from their website and contacted them. That was on April 6th. I got a confirmation of email submission, but since then no reply. Below is a copy of the email I sent:

"I read an article on News24 this morning about the SANBS needing people to donate blood over the Easter weekend, as they generally do, and over most holiday periods. They were referring to the Western Cape, but I know that the other provinces, and also Gauteng, are always asking people to donate to avoid shortages. It was this request that prompted me to contact you. I have been a blood donor since I was 20 years old. In the late 70''s and early 80's (when I was still living in Cape Town) I was also a white cell platelet donor on a regular basis. I am now 72 years old, but since I turned 60 (I live here in Bedfordview, Gauteng), I have been turned away from every blood donation drive that has been held in the shopping centers around me. I am O+, so a universal blood group, fit and healthy, but I get turned away every time I have tried to donate - because of my age. My late father, who passed away at the age of 80 donated blood up until a month before he died (in East London), so I don't see what the age problem is here in Gauteng. When I see these appeals for blood, I feel no sympathy because there is obviously some ************** when it comes to donating blood, so if you have a shortage over times like long weekends and holidays, all I can say is "your fault, - I have been begging to donate but have been turned down every time."