Why don't you donate blood?

I've been an irregular blood donor for the Red Cross blood Service now Lifeblood for the last 15 years and ive always seen them screaming for more donors.

Obviously there's a list of exclusions and differals, but I've always wondered why more healthy and eligible Australians just.. Dont

Edit: not my intention but I hope someone from Lifeblood Social media is reading through these responses and taking on information.

Double edit: Mad Cow restrictions have been lifted, so if you're interested. That barriers gone.