Three main factors imho: The current infotainment systems are not fluid due to saving cost on the chipset. The Android Automotive platform will only soon hit many new models by many different manufacturers as it takes a few years to decelop a new car. The shitty UX is mostly hampered by legal guideline nightmares you’ll have to stick to (which phone manufacturers don’t have to).

Not trying to make excuses here, I’m only using Android Auto as well lol