Having spent time around "sinners" and also around purported saints, I have a hunch why Jesus spent so much time with the former group: I think he preferred their company. Because the sinners were honest about themselves and had no pretense, Jesus could deal with them. In contrast, the saints put on airs, judged him, and sought to catch him in a moral trap. In the end it was the saints, not the sinners, who arrested Jesus.