Comment by HPsquared
They still do, I believe. Cars usually have several antennas embedded in e.g. the rear glass. Even something like the FM radio often has 3+ antennas in different locations and the receiver switches between them to get the best signal. One shark fin isn't enough.
Now shark fins are in vogue again because they house multiple antennas — FM/AM, DAB, GPS, and recently more importantly, 4G. Maybe even WiFi — weird as it sounds, I saw some strings for WiFi antennas in a popular stock media/head unit’s firmware.
Though you are probably right and many cars with just FM/AM and DAB still put them in windshields.
I’m not sure about that 3+ antenna claim for FM. Do a fact-check there. ;) I think most diversity antenna systems that you describe use 2. And they are still considered “premium”. 3 is a bit overkill for FM, FM is very resilient against obstacles.
If I’m wrong, would be interesting to see an example of a car that uses 3 or more. Probably far outside of my pay grade to say the least.