In my years of working with people to establish quality turf and control many of its problems, I have come across many misconceptions people have about lawn establishment and control.
Misconception Number 1: Not bagging grass contributes to thatch.
Although you do not want clippings to become so extreme as to prevent sunlight from reaching the blades, finely ground and scattered clippings can contribute as fertilizer. They do not contribute to thatch as these clippings are mostly water and they break down quickly.