I agree with you OP, but the benefits are for the children.
It is a hard balance to strike as we don't want to make things so easy that we encourage people to have lots of children who they can't look after or provide for, and yet the number of children in poverty has increased exponentially in the last 14 years- largely not due to people having lots of children but due to wages falling behind the cost of living, Tories being the usual Tories and many people who actually work cannot afford basic things and need state hand outs. Work should pay and this is fundamentally wrong. The state is effectively subsidising employers. Things have started to catch up a bit in the last year or so but there is a lot of catching up to do, and the energy prices have been and are still utterly ridiculous.
One change I would personally make is come down a lot harder on absent parents who don't provide for their kids, go self-employed, hide money etc. The state is picking up the pieces in many cases for feckless (mostly) men.
At the same time the birth rate is 1.1 or something. Clearly the global population is huge but in actually only a small minority of countries now it is high. This should change if women and girls are allowed to stay in education longer - a number of charities and NGOs are trying to make these long term changes. While so many people mean a lot of resources are used/will run out most countries also have a young/old imbalance.
Then there is a question: Who should have kids? My answer would always be whoever wants them.
Then there is the perpetual elephant in the room - immigration. We do feel like a crowded country sometimes, and successive governments have not invested in enough infrastructure to deal with the growing population. But if lots of young people do come here, live and work, form countries with a young population that kind of sorts out the age imbalance. Then again building more infrastructure impacts on the environment and are we not then just contributing to climate change. No easy answers.
Other than pursuing feckless fathers- that could be done. Likely MPs are among them though so it would be turkeys voting for Christmas.