People will do things they see other people doing. In uncertain situations, we assume the crowd knows best. This is the "herd instinct."
Published in 1984 (and updated in the 2021 expanded edition), Influence is not a "get rich quick" scheme. It is a behavioral science classic. Cialdini, a Professor of Psychology at Arizona State University, spent three years going undercover—training as a used-car salesman, a fundraiser, and a telemarketer—to find out what makes people comply. Influence The Psychology of Persuasion robert cialdini pdf
Cialdini argues that we are biologically wired to repay debts. If a friend invites you to dinner, you feel obliged to invite them back. If a charity sends you a free packet of address labels, you feel guilty throwing away the donation request. People will do things they see other people doing