Could you give one, just one, example of a benefit to the pax? I mean an actual benefit, not the kind of benefit that marketing people invent.

For example, you mentioned "the ease of single ticketing." How exactly is that a benefit of codesharing? I have so far never encountered the situation where I can get a single ticket if I book a connection on a codeshare but where separate tickets are required if booking the same connecting flight under its "real code." Thus, the benefit of single ticketing seems totally unrelated to codesharing.