SC - OOP pie crust question

[Bonne of Traquair]

Contemplating Thanksgiving pies and was wondering if someone has an 
explanation for why several of the modern piecrust recipes I've 
accumulated call for small amounts of vinegar (one says vinegar or lemon 
juice).  I have two versions of this, and I think the other unusual thing 
they both call for is an egg, so maybe that has something to do with it???

What would happen if I left this ingredient out of this style of crust?  
Since I have a serious ascetic acid sensitivity to cater to, I can't use 
the vinegar; the lemon juice alternative is acceptable, he says.

Thanks,
Chimene