Cupping helps draw out unnecessary substances from the body, it's a great way to detox and relief muscle tensions. For example, if you are a swimmer, you're soaked in water and chlorine frequently, so, in Chinese medicine philosophy, there could be too much dampness in the body, or chlorine toxicity. Cupping can help with these conditions. It might not directly help you keep your mind "focused," but detox and muscle tension relief in general can help you feel more relaxed and clean - hence indirectly affect your mood/focus. But usually, cupping is not associated with mind focusing if that's what you're asking.
Hope I've answered your questions.