When an agent resigns, the stated reason is usually commission: a competitor offered a better split, a cap, or a revenue share. It is the easiest reason to say out loud because it is impersonal and unarguable.
Press further and the pattern changes. The agents who move are almost always the ones who stopped growing. They were not getting listings from the brokerage, they were doing their own transaction paperwork, and nobody had reviewed their numbers with them in a year. A better split is the excuse that makes leaving feel rational.
That distinction matters because it changes the fix. If splits were the real cause, you would compete on margin forever. If support is the cause, you can win without giving away economics.