I suspect the issue is the light bulb form factor. That shape requires that each fixture have its own (cheap) voltage regulator, and badly hampers their ability

I suspect the issue is the light bulb form factor. That shape requires that each fixture have its own (cheap) voltage regulator, and badly hampers their ability to release heat. If you look at new residential light fixtures at your home improvement store, you’ll notice that they’re starting to shift over to built in LEDs. This allows them to use larger and better thermally regulated power supplies, and to provide better airflow over the individual LEDS. I actually believe that the light bulb form factor is going to end up dying out in our lifetime.