Have more than a few dealer clients who don't list sale prices online - just the expected monthly payment, or something along those lines.
I don't want to sound silly, but I think this problem starts with Car Classifieds like Autotrader, CarGurus, and other platforms alike.
What I mean by that is... some of these platforms are designed to cannibalize dealerships on their vehicle prices. So those with the lowest prices rank higher for a specific make/year/model of vehicle within a specified region.
Dealers front-end margins have rapidly declined year after year, so for a dealership to prevent the listing of prices isn't really too condemnable, IMO.