The DM doesn’t necessarily have your modifiers memorized and asking what they are every time slows down play.
Pen and paper or even a tablet exist for a reason. Having the key stats of your player characters stuck up to your GM screen or open on your second monitor is about the best use of space there is.
Besides, it doesn't take much brain power to put together that making the rogue who's been making short work of locks the past month roll for a simple lock under no time pressure is just silly. I get if an AL GM doesn't know the characters but for majority of weekly groups' GMs this is an absolute non-issue.