In the case of Ticketmaster, the reason you have to type these characters is to prevent scalpers from writing a program that can buy millions of tickets, two at a time.
Npr., u slučaju Ticketmastera, razlog zbog kojeg morate tipkati te iskrivljene znakove jest da se spriječe preprodavači da napišu program koji može kupiti milijune ulaznica, dvije odjednom.