It's perhaps a shortcoming of the medium – lack of time – and to keep the script short & engaging for the viewers. In a similar vein, computer nerds are shown to write code or hack systems in no time, when in reality a lot of high-concentration hours are burned, but from the outside watching someone stare at a screen doing not much other than think just isn't that exciting, and in the same way chess games ending in draws again and again aren't that exciting to watch for lay viewers. Also, films like that tend to ignore the "team" element (whether it's in sports or computing) and tend to over-emphasize the single protagonist "genius", also unrealistic.