After delivering the most sacred promise of the Gita, Krishna immediately places a boundary around it. This teaching is not for everyone — or more precisely, it should not be given to those who are not ready to receive it.
Four types are named: the person with no discipline, the person with no devotion, the person who has no desire to listen, and the person who bears resentment toward Krishna. These are not permanent labels on anyone. They describe states of readiness. A seed placed on stone will not sprout — not because the seed is flawed, but because the ground is not ready.
This restriction comes from care, not exclusion. Sharing sacred knowledge with someone who will misunderstand, dismiss, or mock it harms both the teaching and the listener. Krishna is protecting the integrity of the message and the well-being of the person.