If everyone practiced all eight limbs of yoga, it would lead to world peace, but since most are not even practicing one limb (hatha yoga of body positions and stretches) then the conditions we see remain the same. There is no overall trend to peace and challenges that lay ahead that will test the mettle of peace keeping to the max. The question of peace is more deep seated than mere wishful thinking and involves the innermost thoughts and desires of each and every one of us. It will take a majority of us acting in peace to move us over the tipping point to peace.
There are also many misconceptions about spiritual yoga that lead people to false ideas. Unfortunately, very few are aware or know of Patanjali, the one who is considered the guru that transmitted the ideas to us in current times. Yoga is of course far older than Patanjali. He wrote down the concepts and ideas that are available to read today on the full subject of yoga in all of its forms. A few practitioners is not enough to take us over the tipping point.
If we stand back and look at the world of humanity objectively, we see that instead of going toward peace, we are at war and occupied with civil unrest in many parts of the globe.