There is no need to tip. It is a custom in Europe and America to tip after receiving service. I remember knowing a girl who worked as a pedicure technician in a foot bath shop a few years ago. A foreigner gave her a tip of 50 dollars. But we seldom tip here. Of course, it is normal to massage and tip. Guests feel very comfortable and relaxed after the massage, so it is reasonable to tip the technician as a reward.