There's no motive other than "easy politicial win". The kids aren't gonna vote against you (they don't vote), parents will vote for you, you get to show people you protected children and passed legislation. Politicians support anything that keeps them in votes and campaign contributions.

Kids dont vote, but when they do they tend to come in radicalised and swinging. Voter intention in Australia has shifted heavily towards minor parties over the last decade. While this is currently being captured by our preferential voting system, the tipping point is 1 - 2 elections away.

Isolating kids from current events and society can easily be seen as a potential extra bullwark against changing voter intentions, because Minor partiers tend to favour social media engagement against paying for expensive ads.