Before her third consecutive double shift at a pizzeria last year, Grace Velez pulled her hair, which fell past her waist, into pigtails. Ms. Velez says she was used to inappropriate comments from customers, but what she experienced that day shocked her. Regulars who usually never tipped put money in the pizzeria’s tip jar. A few older men winked at Ms. Velez, 21, as they dropped in cash. Another man, who Ms. Velez guessed was in his 30s, tried to flirt with her for 10 minutes before asking her whether she was a high school student. About halfway through her...