Why news headlines in present simple tense even if the real-time event in the progressive mode?

During demonetization in India, I saw on the television that 'people are waiting in a queue for money'. But in that real-time event, the news headline appeared on television as 'People wait in a queue'. It should be 'people waiting in a queue' – why is it in the present simple tense?
Why are the news headlines in the present simple tense even if the real-time occurrence is in the present progressive mode?