The reason is simple: To interest viewers/readers/listeners (or VRLs later).

If the commercial says "How your child may be affected from playing too many video games?" to VRLs, and the child is playing video games and going through the psychological stereotype of adolescents, this will cause VRLs to view/read/listen (or VRL later).

There are also some other benefits to this. Like on a live audio-visual broadcast on CBS or Fox if they presented this issue, if someone acts violent do to one of there shows, they can use this propagated fragment of a broadcast to divert there attention to video games, thus CBS or Fox has created a scapegoat. This can also happen with radio. The reason it is vidoe games are due to specific circumstances (such as parents ignore video games and let them go by in the background of their lives and the fact they are very popular) allows them to be easily picked on.

In the end though, the reasons why it is vidoe games are large, but the main reason is to have better publicity on a whole.