Apple and Android have made the specific decision to not allow video or audio to automatically play when it is loaded in a page. Their reasoning is it places excessive burden on mobile data networks and chews up data quotas when the user may not have specifically requested to view the content. I believe this is mostly to thwart video banner advertising from loading on page load or hidden video/audio content to play when an unsuspecting link or button has been tapped.
Here is Apple's official technical page that addresses the issue, click here.
Various attempts to work around the issue has been made but is sporadic in behavior and appears Apple makes concerted effort to prevent work arounds in future iOS releases.
In short, the user really just has to do one extra tap to view video or listen to audio. Just that simple.