Teens aren't using periods in their messages, so The New York Times didn't use them in an article

Professor Crystal's observations on the fate of the period are driven in part by frequent visits to high schools across Britain, where he analyzes students' text messagesResearchers at Binghamton University in New York and Rutgers University in New Jersey have also recently noted the period's new semantic forceThey asked 126 undergraduate students to review 16 exchanges, some in text messages, some in handwritten notes, that had one-word affirmative responses (Okay, Sure, Yeah, Yup) Some had periods, while others did not [The New York Times]