By a rule, I do not talk to anyone unless I want to, I am required by law to do so or it is an emergency situation. Wit people I know I make an effort to not ignore them and give them some recognition, even if subject is not interested to me or conversation hit dead end, but strangers? Nah, I am usually ignoring them.
Sometimes, when I am willing to get into conversation but it steers into some idiocy after a while, I am simply walking away or stop talking if that's not the option. In such cases, people's reactions are waaaaaaaaay more entertaining than whatever they have been saying, lol.
Fun fact: it is not a crime to be silent around other people, you do not have to talk just for the sake of having a talk.