What benefit is it to put primer white paint on an exterior surface of a house before applying color paint?

Primer is probably the most important step. Primer acts like an adhesive. It not only bonds to the under surface better than finish coat, but gives the finish coat something to grip to. It has a dull surface which the finish coat loves. You will paint half as often, and see better results. What benefit is it to put primer white paint on an exterior surface of a house before applying color paint?
it fills in voids, allows the new paint to adhere to the old paint, What benefit is it to put primer white paint on an exterior surface of a house before applying color paint?
If you might not have done a good job at preparing the old surface, the primer give you some forgiveness and allows the new paint to adhere to the old paint or surface. Will also even out the base color so your new color will be more consistant over the entire house.
also if your going to paint your house a diffrent color than white have then tint the primer to the color your painting will help with the final coats
The above reasons, plus it will also cover stains and other discolorations that would otherwise bleed or show through.