I've been flying for 22 years now, about 100K-200K per year. Yet, still I do not underestand the reasoning or logic behind the "piece system" for itineraries to/from/via North America.

Why, when I fly on a booking that has no routing to North America, say from Johannesburg to London with British Airways, do I only get 23kg in economy or 40kg in FIRST?

But if I fly onwards to somewhere in North America, then I can bring with me two bags each weighing 32kg regardless of class traveled? That means that a person traveling in economy gets to take 64kg, or 24kg in excess of what a First class passenger gets for a similar trip outside North America!

The aircraft are all the same, afterall.

I tried an internet search and even asked the airlines, but never have received a descent answer. I hope a more frequent and/or seasoned traveler here will have the answer to satisfy my curiousity.