It helps to bind the pastry ingredients together it also adds moisture and richness to to the mixture.
Eggs are primarily binders in pastry. When beaten or whipped, they also provide leavening (rising) as air is captured in the beaten egg and rises as the product bakes.
Egg in the pastry for richness and for the wetness to it is useable Egg in the filling to set the filling so it is not runny
To give the pastry substance and body.
as a binding agent
Yes, but they are not vegan.
Fat and taste i think
make the cake rise
it puffs the product
FLOUR provides the structure
The egg yolk binds the ingredients in the pastry together, enabling them to form a dough
it helps the ingredients to stick together
mainly flour, eggs, water occasionally milk
It is just there for flavor, it has no effect on the flakiness.