Funny you noticed that — I asked the same thing after a routine lab test. Veins are closer to the surface and run at lower pressure, so they’re safer and easier to access. Arteries sit deeper and the blood moves fast, which makes sticking them riskier unless it’s for specialized tests. A nurse once told me it’s partly about control — veins are more forgiving if the needle shifts. I later found a simple explanation here veins vs arteries function that cleared it up. After hearing that, the whole process felt way less mysterious.