At a certain point the semantics of the content get translated into an output format. In a browser it's italic. In an iPod it's ignored. The semantic tags are

At a certain point the semantics of the content get translated into an output format. In a browser it's italic. In an iPod it's ignored. The semantic tags are the means, but output presentation is still the end, and there's certainly no reason to expect that all devices can take the original semantic markup and use CSS or some other mechanism to present it. And because of the semantic meaning we can make the em disappear with confidence.