This is an interesting thread! For me, some of the appeal comes from the control aspect of braces, mainly that someone is using toward me, though for the right person I would be interested in controlling treatment as well. I've never had them, so I have a fascination with what they feel like as well. I also do find them interesting on others as well, such as considering why the brackets are placed how they are (top, middle, bottom of teeth), or knowing why others got them in the first place. When looking at braces on others, I usually like an in-progress smile, meaning one where the braces have been on for a bit but not where the patient is almost done with treatment.
Side note, elastics don't really appeal to me, either on others or as a part of a hypothetical plan for myself. Not sure if others feel the same