Here are three reasons why power-sliding is useful when confronting a ghost:
1: If you're ever faced with a straightway, start power-sliding. You'll notice that it will help, especially with Papu Pyramid's right angles.
2: Take advantage of as many shortcuts as possible. More hidden paths tend to open up if you're at a faster speed, which can be achieved by power-sliding.
3: Also take advantage of wide paths, such as those in Sewer Speedway. They can enable you to initiate a power-slide, which can help you gain speed on the ghost.
If you see me posting, it's because I've been asked to. Which I guess would mean I'm taking requests.