More to do with Hollywood wanting a short easy story.
Much detail about the huge operation that did not involve the Turing character directly was left out or reduced. Most in the UK who have read anything about the use of cryptography in the second world war know about the Polish contribution.
I've read most of Kahn's history of code breaking (2006 edition) which was originally written before the Bletchly Park project was publically acknowledged and I found out about the US cracking of Japanese codes using machine assistance but not what we would recognise now as an electronic computer. Kahn's book is handy for historical depth - this whole cryptography/cryptanalysis thing has been something of an arms race from the invention of radio onwards.
I loved how they made it look like known plaintext cryptanalysis was some kind of breakthrough months in the process when the reality is that was the job description - the initial premise of bringing him onboard was based partially on that. KPAs date back to at least the 1800s and were at least well-documented by then, if not also well known.
But really, that lovely movie messed with the timeline all over the place. I talked with the screenwriter at the Hammer museum about it ... he said "it makes a better story" without any reservations. I had to agree.
Better stories should not trump accuracy. After all future generations are likely to see this 'better story' as the real one, such accuracy should be preserved where possible.
