NFL games on Thanksgiving is a tradition that dates back all the way to the first season of the league's existence, in 1920.
The NFL had six games on Thanksgiving that first season. Over the years the tradition as we know it took shape: The Detroit Lions hosted their first Thanksgiving game in 1934 as a way for the team to drum up attendance, the Dallas Cowboys happily volunteered to be the host of a second game starting in 1966 and the league added a third rotating game for Thanksgiving night in 2006.
The NFL has become a staple for the holiday.