Or the car just doesn’t start one day because it hasn’t connected to its server in a month, forcing you >to go to the dealer to fix it.
You are exaggerating, a manufacturer can't do that. The simple reason is that lots of people live (or spend part of the year) in places where the only internet access is through satellite, this is specially true in big countries. The most probable thing they do is to save all the data until there is internet connection available to send it.