Your suggestion has at least two severe issues:

• It doesn't scale. The people that can and want to "wait until they're ready" probably are doing that already. Meanwhile, the large, unwashed majority does whatever they feel like, and why would they want that to change?
• It takes away personal liberty and punishes people who "cannot control themselves," giving way to social authoritarianism. To me, that's the exact opposite of what any elected government should do: to make people's lives better.