Why do people say the Cowboys have the most bandwagon fans in the NFL?

That is definitely not true they haven't been great this past decade yet they are still the most popular team in the NFL they are always number 1 or number 2 every year in merchandise sales they easily have the most fans in the NFL and yet people seem to call every Cowboys fan a bandwagon fans. These fans are way more loyal than most Steelers fans. Where were all the steelers fan before 2007.