There's a technology issue too: my German in laws gave us a baby carriage that seemed to have been built for ascending the Eiger -- though it seemed (and was) huge it made navigating Paris quite easy (had to carry it up/down the metro steps) and even fit in the prehistoric elevator in our apartment building. Frankly, supposedly-snooty parisians are quite accommodating towards people with babies (once they can walk on their own though...)

But I never saw anything like that in the parisian baby shops.

I agree though about unattended obstacles on the trottoir -- it's as if people forget they need to use them themselves.