One might note here that not all robots are created equal. Robots dependent on machine vision to function would need a lighted factory similarly to humans.
And more interestingly, there might be value in isolated sections of the factory being climate-controlled to very different temperatures, depending on the particular robot in use. Not like these things walk around between stations.
In the long run it would still probably be cheaper to have infrared cameras or a few LED rings around the camera lense rather than full on industrial grade lighting 365 days in the year.