Most people are squeamish about blood.
They don't want to see it, think about it, or talk about it. If instead of dying on the cross, Jesus Christ had donated a pint every two months during His adult life, He would have given much more blood, but it wouldn't have done us any good. Every person who heard those words understood the story of the Passover Lamb, whose blood was put on the lintel and doorposts of the dwellings of the Israelites in Egypt. They remembered how the destroying angel had killed every firstborn child in Egypt who was not in a home protected by the blood of the lamb. We encourage you to read the New Testament seriously for yourself, especially John or Luke.