Is it normal for my bf to flirt with customers?

My boyfriend (22M) works as a bartender near a college campus. Since a lot of the customers are around his age, it's pretty common for people to flirt with him while he's working. He usually flirts back because he says it helps him earn better tips, which I can understand to a degree. He doesn't give out his number, go home with anyone, or get physical with customers, but he does lean into the flirting quite a bit. Is this normal for bartenders, or should I be concerned?