So that you can't suspend disbelief. I watched that Zac Efron Ted Bundy film last night. Zac was passable but the move would have been better if he did a bit of dancing but I digress.
The woman playing his girlfriend was awful, staggeringly so. I googled and aparently its Lily Collins. For a start she looked far too young, not her fault but that of the casting person. She just didn't have the gravitas to pull off the emotion of finding out your partner is a serial killer, even in a cheesy movie.
I know there's others. How do they get cast when there must be so many talented actors around. Is it why Brits get cast in the US so much?