After the extinction of humanity, many vehicle types weren't useful or tolerated anymore. This led to many of them following the humans into extinction.
Too slow to run from planes. Unable to move on the ground. Eventually, the few factories left that produced them were all destroyed.
Phased out after WWII, due to being very limited in their uses.
Wheeled Fighting Vehicles
Not strong enough. No factories produce them anymore nowadays.
Half-Tracks and Motorcycles
Were never sentient in the first place.
Too specialized. When planes became rarer, converting to this vehicle type wasn't viable anymore.
No use. Were hunted down for sport at the very beginning of the age of machines, and very soon none were left.
Became obsolete since TRVs can do their job.