Fashion has a natural cycle of its own, which is more dependent on market and media forces than seasons or weather. Trends are predicted, recycled, set and followed. Seasons in fashion have shifted, designs are made and sold 'unnaturally' early. You can buy your new winter coat when it's still warm outside and the leaves have yet to fall from the trees.
Though there are people that have a big influence in the world of fashion, it can never be entirely controlled – certainly for the individual consumer, his or her influence is nil. Styles in fashion each have their own life cycle, they go in and out of fashion. Though when they re-emerge evolution is visible. And so, yes, even shoulder pads come back.