I don't think this is true. I find the poor are the ones who overpack, because they have not the experience of traveling to know what they need and don't need. I certainly would love to travel with only one bag less than 23kg, because I know half of what I would want to pack, I generally never use when traveling...

But as it is, I often end carrying more for other people whenever I fly long-haul and/or shipping new own things (i.e. upcoming trip to reposition ski equipment from Seattle to Europe). Upcoming trip next week one entire suitcase is devoted to gifts alone, and half the other one is things for my parents. Lugging Christmas presents, presents from other people, clothing for other people (I always come back from the US with a Gap shipment for those deprived in the Netherlands), new cloths for myself, new books, old books (books weigh a lot), whatever... I'm not a business traveler obviously. When I do travel "on business" it is indeed only with a small suitcase.

If I take out everything not related purely to my immediate travel needs, I'd probably only have 20kg maximum. I also have wardrobes in three countries, so that helps. Poor people don't have wardrobes in three countries (not that I'm rich by any stretch of the imagination).