Today, I have an appointment to have a hairtrim. Why do we use a blow dryer to reset the "do" when we're going to see someone who will re-do it anyway?
It's like vacuuming the house really well before the carpet steamer people come to do it thoroughly. Not very useful, but we do it anyway.
Or, how about brushing the cat an extra long time before she goes to the vet's office for boarding. The first thing they will do is give her a bath. Well, I can see a reason for all that pre-brushing. Who wants to be responsible for embarrassing the cat?