Noticed today when poking through the Drop Shop. Not limited to any one brand. (Giant has several models with missing rotors but visible calipers, others with rotors present)
EDIT - It appears road & TT bikes are missing rotors. Gravel bikes and MTBs have rotors still.
Also, some bikes may have odd names:
E.g.: “Zwift 2023 Zwift Academy Bike Paint” and “Giant TCR BikeExchange-Jayco Team”. (or were those always named thusly?)