It's not really for you - it is child benefit, after all. Think of it as basic income for kids, to keep them clothed and out of the factories.

I'm in favour of bringing back the Education Maintenance Allowance, and making it very slightly performance-related.

The government has interest in people investing in future growth (children), so it's subsidized. The alternative would be to tax childless people more heavily so they are always revenue-neutral with respect to retirement, health, and disability benefits.

In UK? You always qualify, but you'll have to pay it all back if your income goes over a threshold. In its current form, it's basically an interest-free loan for 12 months.