The lawyers job is to persuade the trier of fact that his or her point view is the correct. Words often are expressed without full comprehension by the listener. Communication can readily occur by presenting images and graphics. Graphics, of course, are no stranger to the courtroom. Graphics programs help prevent last minute trial exhibit preparation.
Local rules are likely to require disclosure of charts to the opposition at an early date.
What frequently happens is that counsel will tell opposing counsel that they expect to have a blowup or a graphical presentation available at the trial but not have one to show opposing counsel. There are several reasons for delay in preparing graphical presentations. Blowups cost money to create, both in terms of material costs and lawyers time. Graphics usually take time to prepare. That time might be better allocated to other aspects of trial preparation.