If you live in a suburb of Paris, even close one - you have at least one car (often two + motorcycle for when there is too much traffic). And you go to Paris once a year maybe. But a lot of additional transport linking suburbs and Paris is coming up, we'll see how it plays
Maybe don't exagerrate things... When I was there, we would go to Paris at least once or twice a month. And I am sure without a car in the Petite Couronne would be no big deal.
I do not think I am exaggerating - I do not know your situation, but when I spent two years in petite couronne - I was pretty much like you describe (no car, going to Paris regularly). And it was a nightmare - got back to living in Paris.
Families with kids in suburbs have about as much interest in going to Paris as Southbank Parisian families going to North Paris. All they need is around then - schools, hypermarkets, IKEA...
90% of people I worked with over last fifteen years in four different companies live in suburbs - and they mostly fit the description. Kids and their activities take you a lot of time, car is very convenient etc what reason would you have to go to Paris instead of spending a weekend in Normandy 🤷♂️
There are less museums in Normandie. Maybe you can accept there are different people with different tastes... And different places in the banlieue. My point is, the infrastructure is there and growing. Stop exagerrating how bad things are.
Sure, I accept that there are very different people. My observation is just my observation 🤷♂️ And the fact that most people spend time very close to where they live is not "bad, IMO it's just reality. Also, it's also kind of good since it means you have access to all necessary infrastructure close