Hs OC here.
we do it to:
1) give players confidence and being comfortable on the first drive when nerves are flying high. (They’ve practice that same sequence of calls/formations all week)
2) MAKE SURE that you get in formations and plays you want to see early to make defense show you their hand. You take what the defense has done to your first script which then lets you manipulate the defense by alignment/matchups.
3) Helps the playcaller use the actual gameplan. You would be surprise how incredibly quick you have to be getting the next play call in. That way they don’t just go to old faithful every time.
4) if it’s a well coached opponent then you know they scouted your film for tendencies. If you are a good staff you do a self scout as well so you know what tendencies you showed. You take their defense and then have some kind of idea what they should do to you and allows you to prepare for it. So you give them the pre snap look of a tendency you have showed last week and then hit them with the counter, knowing you know that they know. (If that makes sense)
That’s just my first thoughts but this is an hour long clinic talk on why to script early plays.