If you just sit up higher or move out to the side and catch more wind, and/or shift into a bigger gear, that tends to slow you down, and allows you to keep pedalling. If you start coasting, when the speed picks back up, you take too long to react, and then you cause a whiplike effect on the whole paceline. That forces everyone to break, and then over-react to get back up to speed. Then when they hit the front, their legs aren't fresh. This is why you shouldn't coast in a paceline.