I think this all happens because buyers tend to greatly overestimate value of those small features. Initially, producer will devise a new feature to differentia

I think this all happens because buyers tend to greatly overestimate value of those small features. Initially, producer will devise a new feature to differentiate from competition. Later, competition will feel pressure to keep parity and so they will also include it. It becomes a standard and nobody will sell a car without the feature. That's how you get a car laden with heaps of marginally useful features.