This very much feels like "in addition to" rather than replacing a car, at least in the US. My wife and I (without kids) tried living without a car in one of the largest, most walkable cities in the US and it was doable, but it's just soooo much nicer to have a car. Coordinating rentals or even ride shares are a lot more tedious than jumping in a car and driving, and even if ride shares are cheaper than car ownership, I would often find myself not doing things because of the cost of ride share / car rental / etc. Further, I would have occasional ride share drivers blow me off when I really needed to be punctual, and I also had some fraudulent experiences with car share companies (upcharging me for services that I've explicitly declined and not correcting it via customer support channels).

There's also public transit, but that takes wayyyy longer to get around and it's also really dirty, crime-y, and otherwise uncomfortable at least in the cities I've traveled around in.

Lastly, cycling is probably always going to be less safe than getting around by car (we can and should improve cycling safety, but I don't know that we're ever going to get to parity with driving) and I don't know that very many people are going to want to subject their kids to that risk as their primary form of transit. I probably wouldn't, realistically.