We will put stage directions instead of a lot of dialogue because too much dialogue can make the play very boring this is shown in the first episode of young Dracula of the script http://www.bbc.co.uk/writersroom/insight/childrens_drama.shtml  
On the first scene part one of the script it shows very less dialogue but instead it shows a lot stage directions this is useful because as it's the first scene it'd want to grab the audiences attention and not bore them.