Omission bias

Omission bias is the tendency to favor an act of omission (inaction) over one of commission (action). It can occur due to a number of processes, including psychological inertia, the perception of transaction costs, and a tendency to judge harmful actions as worse, or less moral, than equally harmful omissions (inactions). It is controversial as to whether omission bias is a cognitive bias or is often rational. The bias is often showcased through the trolley problem and has also been described as an explanation for the endowment effect and status quo bias.
Examples and applications.
Spranca, Minsk and Baron extended the omission bias to judgments of morality of choices. In one scenario, John, a tennis player, would be facing a tough opponent the next day in a decisive match. John knows his opponent is allergic to a food substance. Subjects were presented with two conditions: John recommends the food containing the allergen to hurt his opponent's performance, or the opponent himself orders the allergenic food, and John says nothing. A majority of people judged that John's action of recommending the allergenic food as being more immoral than John's inaction of not informing the opponent of the allergenic substance.
The effect has also held in real world athletic arenas: NBA statistics showcased referees called 50 percent fewer fouls in the final moments of close games.
An additional real-world example is when parents decide not to vaccinate their children because of the potential chance of death—even when the probability the vaccination will cause death is much less likely than death from the disease prevented.