Scalp protector also does what it says on the tin.
It protects the scalp for being irritated by the base and the glues & tapes.

It has the side benefit of helping adhesion because it can form a barrier between the skin producing oils & moisture and the bond.
So it works both ways, things seeping in to the scalp skin & things seeping out of it as well as any friction.
As you attach quite regularly, you're not looking for a long bond, but you may be benefiting from it protecting the skin.

Using alcohol to remove any vestiges of oils or grease will always help a bond, but if you notice no difference between when you use it and when you don't, then its a waste of your time using it frequently.