Here in SE Asia where turbulence is a common occurrence I've had a number of flights where they will announce prior to take off that they will not be serving hot drinks "due to weather conditions" . The flights have turned out relatively uneventful and the flight attendants still get up to serve meals and water. Agree with others that the threshold for US airlines to turn on the seatbelt sign or reduce service is low. If the flight attendants were up, there's no good reason they couldn't sling a croissant at the business class passengers at a minimum.