The PowerWall is a great product for what it is, but Lithium Ion is wasted in a permanent install. Other battery technologies are more reliable, cheaper, safer and simpler.

The only thing Lithium Ion has going is ubiquity due to volumes of scale. It is like putting a ESP32 in something that needs to be connected to the internet because it is cheaper than a separate microcontroller chip and ethernet chip; or how most Lightning headphones use Bluetooth because a single Bluetooth chip with integrated DAC is cheaper and more readily available than an official (or even a bootleg) Lightning chip and a DAC chip.