Adding more rotating parts is exactly what you are trying to avoid. For example, go look at how Tesla designed the heating and cooling system. The integrated all the different streams of hot and cold in one system duplicate these parts that can break easily.
In some cases it can simply not be avoided of course but you better make sure that you really need it if you are gone add it to millions of cars.
> cruise and waymo and co have multiple units per vehicle and collectively hundreds of thousands of vehicles
Waymo has vehicle count of a few 1000s as far as I know. I don't know about cruise but I don't think the have even 100k vehicles. Please show me a source.
And even if that were the case, the build those fleets of quite a long time and the cost per vehicle they currently have is nowhere near close to what would be possible for a car like the Model 3 or future cheaper models.
Margins in car industry are incredibly tight, car companies invest gigantic amount of capital to remove a few $ per car. These vehicles need to be able to be produced at a run rate of millions per year. If you are proposing to add something that cost 100-1000$ that is a absolute killer.
In addition its an additional part that can hold up your production. This current chip shortage is a perfect example where having a Lidar would just introduce a whole host of new chips that might be in a shortage.