Like attracts like.
Watch how other people with the same model cars will always try to park next to each other when they have the choice.
People with similar cars wave; it's awkward.
Apparently Jeep owners in particular have a culture of recognizing each other on the road.
Jaguar owners only nod at each other, very discretely.
Before daytime running lights it was customary for SAAB owners in the 70's - 80's to flash their headlights at each other.
I like watching people when shopping.
I like watching people period.
They are fascinating...and scary many times too.