See, I'd almost see that the other way around, that it's easier for kids in a city with good public transport links because they can get around without having to drive. I live in a medium-sized city in Germany, and kids here can be really independent - you'll regularly see them on the trams in the morning going to school, or hanging out with friends in public spaces. My wife, who grew up here, used to make plans with her friend every summer where they'd figure out all the summer activities they wanted to do and how they'd get there and which buses they needed to take, and then they were basically set free to do that.

The other aspect is having things to do. A backyard is nice, but we have so many parks and playgrounds and cafes and museums and kids' clubs within 15-20 minutes of us that I don't think there's any danger of kids getting bored. And all of that is available on foot or by tram. With the Deutschland-Ticket in Germany, you don't even need to worry about tickets, just hop in and go. As someone who moved here from the UK where these sorts of cities are much less common, the high density and accessible public transport is one of the reasons my wife and I ended up staying here to have children rather than moving back to the UK.