In poker, we don't tap the glass because it disturbs the fish. If the worst player at the table leaves, that hurts everyone since we win money directly from the other players. But blackjack is banked by the house, so one ploppy leaving won't directly hurt us. But if there's a whale at the table playing badly, you want him to stay. They're unlikely to back off a counter betting smaller on average than the whale at the same table, because the whale might leave and never return if he thinks they'll kick him out for winning. The counter wins less than the whale loses.