The evolutionary mistake that allowed us to walk on our feet and use our hands enabled us to build tools, conquer our environment and tackle hard problems. A humanoid robot provides a good blueprint for creating a robot that can do anything.

A solar field robot can only do one thing. A humanoid robot with a software model that allows it to install solar fields and then switch to a new model is a much more compelling use case. Eventually you're going to run out of solar fields to install, then you need a solar field repair bot, a solar field cleaning bot, etc. General purpose robots that can switch models to perform different tasks is not a dead end, but definitely a very hard problem.