The more we learn about the human body and different populations of people, the better we can understand what we should and shouldn't be doing. Human movement is a complex orchestra of contributing tissues and structures. If one aspect is sub optimal then the effects can cascade throughout the body. We look for certain pre-requisite capacities on a local level before we can trust the movement as a whole will be sucesful!
Here's a link to an article I contributed to for Canadian Trail Running Magazine where I discuss the effects ankle mobility has on your knees and even your hips!