Rat 5.
Don't you remember the good old days when the airlines, in IATA, would meet and agree common standards for just about everything. Baggage was no exception and included weight/piece rules for carry-on and checked bags. Even had common rules for charging for excess baggage - often not cheap. But much more convenient than shipping as cargo.
Even the non-IATA airlines followed the standards because, well, why reinvent the wheel?
Then governments, primarily European ones, the U.S., Australia and others decided all of this coordination was anti-competitive. So it stopped. IATA still exists but ther is little standard setting they can do. More often it's done in the alliances where they have limited anti-trust immunity.
Many would say we are better off with a free for all.