Because the US, like all carrier-operating navies, DOES enforce an exclusion-zone around their ACCs. If it was such a common occurrence such incidents wouldn't be news-worthy, would they?
Depends on what you mean by "news-worthy". You don't see this all over the evening news, or the headlines of national dailies, do you? You see it in a defence blog, then picked up by other defence enthusiasts.
The ploriferation of blogs and the internet has made the distinction between 'news' and 'information' non existent, and therefore terms like "news-worthy" don't mean the same thing anymore. If we are to judge the importance of events by their "news worthiness", and by that if you mean its appearance in blogs and other websites or even online pages of news channels, then the latest incidence of a celebrity's skirt moving a wee bit too high would be a hundred times more important.
Navies do snoop on the assets of other navies, and maintain a database of electronic and accoustic signatures. And buzzing by elint aircrafts is common on the high seas. There is nothing to be done about it, if it happens in international waters. If it was in our maritime zone or airspace, that is a different issue.