When withdrawing blood from an artery, why do techs use a booklet method?

When drawing blood from veins they use an automatic vaccum suctioning tube, but not beside arteries. Or can they ever use vaccuming with arteries? It have to do with the reality that the blood coming from veins within order to win to the heart, it has to row gravity; this is done with the relieve of valves –i.e. the leg valve http://sln.fi.edu/biosci/vessels/veins.h. .Therefore, the blood coming from them [veins] do not flow as easy as the one coming from the arteries –which flows out from the aorta to the rest of the body next to the full force provided by the strong pumping action of the heart. That’s why in that is no need to use a vacuum for arterial blood collection.