Pretty much what Nanya said. I understand that the movies were done purely for the Fate fans, which was why she was the only character to not only keep her major scenes, but also get more development. In the first movie, the title character Nanoha gets exactly 0 backstory. In the series, she at least got some backstory and reasoning for actions, in the form of her history with Arisa and Suzuka. This is important, because it was that interaction which gave her the motivation to reach out to Fate. Without it, her actions make less sense. One of the common complaints leveled at Nanoha is that she seems too mature, but her Arisa/Suzuka interaction, and the issue with her father's injury, were the prime reasons as to *why* she turned out that way. The 1st movie could have added them fairly easily, trimming some time off the Precia/Fate/Linith backstory (hell, at least trim Linith out).
The 2nd movie further removed any development from Lindy and Chrono, who had a very personal connection to the book which was never really addressed or resolved. It was kinda brought up... and left hanging. Much like Fate, Chrono was left emotionally scarred from a trauma when he was young. Unlike Fate, he gets no development or resolution to it.
And the 2nd movie also develops a huge plot hole in the form of the Wolks memories. In the series, via Vita, we learn that their memories have holes... hence why they had no way of knowing that completing the book was bad news. In the movie, it's actually reinforced that their memories are intact, and thus makes it look like the Wolks are carrying idiot balls since they are still trying to complete the book, despite knowing what it will do to Hayate. They know about NachtWal, and know it will take over. Let's be clear that the series Wolks actions are understandable, since they don't want to trust others and know that the TSAB is out to get stop them. They carry a hope that completing the book will save Hayate, and so they just need to hold out that long. In the movie, they should have known that completing the book will NOT save Hayate... thus their only option would have been to seek help from elsewhere. The big key difference is how their memories are treated, which makes them work in A's, but not in the movie.