Alexandra Daddario was too old
... to be playing Blake, I mean. When I saw the movie, I immediately saw that the age difference between her and Carla Gugino and Dwayne Johnson wasn't big enough for them to be parents/daughter, so I went in here (IMDb) to check, and sure enough - when Alexandra was born, Dwayne Johnson was 13 and Carla Gugino was 14.
It is of course possible to suspend disbelief and say that they became parents at a very young age, but it would have been more credible with a younger actress.
Why do you people think the casting people went for Daddario to portray The Rock's daughter?