After a cycle of about 15-45 minutes the performer is usually finished for a while. He can be much more withdrawn than the performer. It's not necessarily to his advantage for people to gather around him. He's not really intending to amass that sort of energy and may not feel up to being the focal point of it. With his instrument he mainly works to passersby and wants people to notice just enough for appreciation and a coin, but to stay in their flow.
Street players earn money more slowly, but more steadily.
They can play in places unsuitable for the street performers. The discreet street player will often be left alone by the police where a street performer would immediately be stopped. There's a lot more tension created when you gather a crowd. More possibility for a happening and quick money, but more risk of conflict from all the sedentaries, especially due to blocking the passages. Usually street players rely on their practice, technique and endurance while the performers rely on inspiration and more surprising expressions.