If I have to guess, I think they are probably on different systems. As roadside assistance pre-dates smart cars, and satellite in general has pretty bad receptions under a roof.
What it boils down to is why would a company spend money so a small percentage of tech enthusiasts who buy their cars can use advanced features for free.
Because "laws".
Of course, there is no way to let corporate do good on its own. Corporates will never respects its user, the environment, and basic consumer rights; if they are left to operate on their own.
If the EU can force apple to care a little bit about the environment and basic consumer rights, then they probably can let the car companies do the same.