I don't understand this mentality. Who told you that you need to own a home to have kids? I don't understand this connection that everyone seems to be making. To me it sounds like an excuse.
You don't necessarily need to own a home, but I think we'd agree most want to be in a good place financially before raising kids. Having a foot on the property ladder and living somewhere you can raise a family over the long-term is clearly part of this for most people.
You're right that couples could just rent a place and try to get on the proper ladder while trying to raise kids, but realistically I think most would want to do things the other way around. But to your point not owning a home is one of the compromises people who really want kids will be forced to make to have them today.
It's a slightly bizarre and under-discussed aspect of British culture. There's a widespread cultural belief that you have to own a house and "get on the property ladder" before you start a family or really consider yourself a proper adult. The ladder is a reference to the assumption that house prices only ever go up so it's free money to own one, which you can then invest in another more expensive house and so on.
You're right that couples could just rent a place and try to get on the proper ladder while trying to raise kids, but realistically I think most would want to do things the other way around. But to your point not owning a home is one of the compromises people who really want kids will be forced to make to have them today.