Why is that? The electricity burned is about the same, no? Of course, the impact is more distributed.

Forget about everything related to the prompt itself being processed for the moment. What other information do you think they are grabbing and processing along with the prompt? Maybe some data about you and your interactions for resale? Account info? Piecing together details about you perhaps, for some of that highly-targeted-advertising-data companies love to sell?

Even the comment you are replying to, IMO, is pretty conservative about the actual energy savings.