Birkenstock sandals have withstood decades of passing fashion fads. Since the 1960s they have adorned the feet of hippies, models, moms, dads and now Gen Z. Birkenstock's success relates to its selectivity in the market. In 2016 it chose to remove its products from the biggest retailer in the world, Amazon. The brand has even found a place in the world of high fashion but turned down a collaboration with streetwear giant Supreme. Whether it's a counterculture statement or a modern day fashion staple, here's why Birkenstocks never go out of style.