Why doesn't Autoplay work in Safari?

Question

css

Why doesn't autoplay youtube work?
How can you get around?

function PlayVideo() {
    $(".js-video").bind('click', function(e) {
        e.preventDefault();
        $(".js-popup").fadeIn();
        $('#video')[0].contentWindow.postMessage('{"event":"command","func":"' + 'playVideo' + '","args":""}', '*');

        $("body").delay(400).addClass("js-modal");
    });
};