Who says the robots have to have batteries?

The market. How many cable powered mobile bipedal robots have you seen?

Human workers drag power cables all over construction sites.

No they don’t? Have you ever been on a construction site? They have power cables, but they aren’t attached to them as they constantly move across a construction site. They are used for a specific job then rolled up and taken to the next job. Dozens of people dragging their own powered chords across a building site would not only be dangerous, but a huge pain in the ass.

but fixed industrial robots have been operating for many decades. The wear issues are obviously solvable in the right context.

As I said in my original statement, laypeople such as yourself tend to underestimate the amount of force a moving object creates. Just engaging in something like jogging can have a ground force reaction of 3x your body weight, something like a small jump can exert up to 7x your body weight. That is with more pliable triplaner joints covered in soft tissues that help reduce that ground reaction by absorbing some of the force with higher degrees of range of motion. Something more rigid like a robotic foot/ankle or prosthetics actually experience much higher degrees of ground reaction force.

They might not even have legs. A welding robot could just be a welding tool on the end of a long boom arm.

The entirety of my argument was around humanoid robots… That’s why I said it would make more sense for a robot on a flat factory floor to have wheels or tracks. I’m not arguing against the idea of robots in general, just bipedal humanoid ones.