Old Media Playing Catch Up
The brilliant thing about the Internet—and the thing that separates it from any other medium or form of communication—is the speed at which information can be passed from person to person and group to group.
Put a link to something cool—a video, a game, anything—on a message board and it can be seen by dozens or even hundreds of people within the next hour. Chances are, many of them will regularly visit other message boards and put the link on there, and so on and so on. A link can go from you to someone else on a board you've never heard of within a matter of minutes, which means that popular internet memes can flare up and die away within days, or grow and grow over the course of months.
Of course, the Old Media are restricted to publication and broadcast dates, which means that (compared to the net, at least) most of the news it delivers is old stuff. But when it comes to the 'net, the issue is exacerbated—most papers and networks are run by older people for whom the Internet is a tool, rather than a pastime, meaning that Internet-related stories can be months (sometimes years) old before they actually make it to transmission.
So while you and your cyberpals may have known about Second Life since its launch in 2003, it wasn't until 2007 — a full four years later — that the UK broadcast and print media jumped onto the bandwagon.
As time goes on, those higher up the media food chain will be replaced by Internet-savvy types, which may destroy this trope completely. As of the mid-late 2010s, however, those who grew up with the Internet through their teenage years are still making their way up the Old Media ladder... and that's assuming Old Media will even still be around by the time those people get the chance to be in charge of them.
Contrast New Media Are Evil, The New Rock and Roll, You Can Panic Now. Compare We're Still Relevant, Dammit!.