The car radio thing only came in here (Oz) in their twilight years just as VCRs and VHS rental became a thing, but it was fabulous to hear a movie IN STEREO! with decent Bass.
Most of the ones that I used to frequent are now shopping centre carparks.
It was sloped at every drive-in I went to - so you’d see over the canteen/projection room.
Half the fun was queueing for burgers, chips (fries), and/or pizza, and coke between the two features. The other half was sneaking beer in. Then the other half was… what was I talking about?