Golden Lion Tamarin's are in danger?

The golden lion tamarin is classified as a member of the order Primates and is a member of the family Callitrichidae. The golden lion tamarin's head and body are about one foot long, and the tail is slightly shorter. It weighs about one and a half pounds. The golden lion tamarin is classified as a critically endangered species due to the fact that it only exists in severely fragmented subpopulations consisting of no more than fifty mature tamarins each, and that there has been continuing decline in the golden lion tamarin population. The golden lion tamarin is one of the most endangered of all mammals. These mammals are endanger becausethere are only a few of them left and not just that people kill them because " bad behavior" but when i read in the info(yahoo) they are completly harmness only if there predator gets close like us. i don't understand why they do this when they can get materials from other things these creatures are pretty they are not meant to be hurt.