I wanted to write something myself but this article seems to sum it up pretty well.
Google, H.264 and Video on the Web
Fact to remember – Chrome is an insignificant browser in terms of market share, Safari and Internet Explorer have way bigger market share on mobile and desktop. However, if Google pulls H.264 support from Youtube, this means you can no longer watch Youtube videos on your current iOS AND ANDROID devices (at least not without sacrificing a crazy amount of battery life. Android devices probably won’t even last an hour with its poor battery life management).