Honestly, I think a big part of it is fear of needles. Sticking a sharp thing into your body hurts, leaves a bruise, and sometimes makes you feel sick. Those im

Honestly, I think a big part of it is fear of needles. Sticking a sharp thing into your body hurts, leaves a bruise, and sometimes makes you feel sick. Those immediate negatives can be hard to weigh against the nebulous benefits of possibly not getting sick months or years from now.