That being said, the National Association of Realtors (NAR) and their local branches are the definition of a cartel. My parents owned a real estate agency when I was growing up in the 80s and 90s. Back then, the cost of selling and marketing real estate was much higher. Most real estate advertising was done in print which the broker paid for out of pocket. Cameras used film back then which meant multiple trips to the property to take nice pictures. Someone had to always be manning the telephone because there were no mobile phones. The listing broker would have to arrange a showing with interested buyers and their broker. MLS was a huge printed catalog you would flip through to look for houses your clients may be interested in.
Nowadays, the cost of listing a house is nominal for a brokerage. Advertising is free because all of the real estate sites that consumers visit (realtor.com, zillow) pull directly from MLS. All cameras are digital so you can take that perfect picture the first time. There are now phone apps that automate broker access to houses to show their clients.
There are all of these productivity improvements for real estate agents on both sides of the negotiating table but the commission structure is almost identical to what it was 30 years ago. I believe the standard commission structure has gone from 7% to 6% in thirty years.