Cover image doesn't show up (mobile, tablet)

Mobile phones have a limitation, that you can't start a video with a code, because of the common usage of mobile internet, and only a user's clicking action can start it. Because of this limitation, we can't put our cover image over the YouTube and other videos, because clicking on the image requires code to start the video, and like this on phones the video wouldn't start. So on phones (and tablets) we are not showing the cover image.