That's true, the arguments were also made for television, movies, radio, and fiction books. However, during the times of movies, television, radio, and written books being introduced, the trend line of student performance seemed to be going upward. It now seems to be trending downward. It's harder to convincingly make the argument that cell phones are no worse than TVs when student performance was increasing during the TV era and is decreasing during the smartphone era. Even if the correlation is totally spurious, it's an uphill climb to ignore it.