Cupping increases the blood flow and warms the skin, which makes makes it easier for the therapist to get into the 'knots' in your muscles. It is a way to work the tissue in a reverse deep tissue method. While the therapist pushes the tissue in the cups pull the tissue up. Allowing the tissue to get a deeper massage with out a lot of discomfort.
2. ... It can then help the therapist to pinpoint exactly where to work and if it needs more work.