I basically feel the same way. I think the writer can make implications about back story using props; I used a picture to imply the death of a parent, certainly actions; a character says, "Hey I've got a sister" when asked why he did something. The former being before the start and the former being after.

I always think about parents, siblings, birth place etc. as a part of the process and then I try to abstract the type of personality by showing their emotional reaction to situations.

I do this in the outline and then I will give that character a "dialog-interaction" frame - where they generally state things in a demanding way or supportive way or inhibiting way and respond to positive or negative interaction prohibitively or angrily or abruptly or sarcastically.

I've been working on a theorem that says using these emotional states leads better to personality which is in fact what people go to see.


So I guess backstory is good for the writer but not for the reader.



The full theorem is basically:
SITUATION sits above
ACTIVE DIALOG\REACTIVE DIALOG and
EMOTION sits above
PERSONALITY

OR

The subtext of the situation is the dialog, the subtext of the dialog is the emotion and the subtext of the emotion is the personality.

Also, this is why I spend so much time on other people's blogs. I've refined several theories with the help of discourse like this.

I write backstory because I have a character behaving in a certain way and I want to know why.

This info does not need to appear in the final script, but I feel my characters come alive and I write better when it's no longer a doll in a dollhouse, but someone's story.