Why can't disposable syringe injection of hand blood vessels

Disposable syringe role often only two, blood, muscle injection and intravenous drug concentration is too high, to organs such as blood vessels and heart stimulation is very big, so I can't but you can't register the backs of hands, and even rarely used for other clinical vein, only need to save, and so on and so forth when will choose this way of injection such as in the arm! Even this time also won't choose hand vein, because there is too thin, easy to wear, and arm vein were also more likely to!
www.medical-supplies.cc