Why are veins important?
They carry deoxygenated blood back to the heart and lungs to pick up more oxygen.
The major vessels that carry blood are the arteries and veins. There are also minute vessels called capillaries.
The arteries carry blood away from the heart and to the rest of the body, where it drops off oxygen and picks up carbon dioxide, which is a by-product of respiration.
Once it has done its job, this particular portion of blood can't be used, since carbon dioxide is useless. The deoxygenated blood is transferred through a series of capillaries from the arteries to the veins, and the veins carry useless blood back to the heart and lungs.
When at the heart and lungs, deoxygenated blood can drop off the carbon dioxide to be exhaled and pick up new oxygen. The blood is like a delivery man, but working both ways.
Without veins, your body would clog up with useless blood and you'd die in minutes.