Apparently, that's more than a lot of actors do. Marlon Brando, Johnny Depp, and Robert Downey Jr, are all well known for not having their line memorized.
Brando is best kn9wn for it, as it was no small secret that he read all his lines from the godfather off of cue cards that where shoved anywhere they could be, while not in the cameras view.
He also killed several people with an ax and burned out the chemical centers of his brain with medical drugs in order to better identify with psychopathic murderers.
Why didn't he brag about ripping up the script and rewriting it randomly on-set like the supposed Harley Quinn writing expert Lady Gaga who definitely isn't completely full of herself and destroyed what that movie could have been?
Also Joaquin Phoenix helped ruin it amd enabled her idiocy.