Audio Durations in TV Commercials

Hey Guys, Currently in Australia every tvc going on free to air tv is required to have half a second of silence at the front and back. (So a 30sec advert has 29 seconds of audio).

I was just wondering if this was a universal style requirement in other countries?

I'm feeling this is a pretty outdated requirement, as I believe it is legacy of some sort of analog workflow.



Cheers

Dave