Why do dance teachers make so little?

Also why are they just part time workers? I have a friend whose life is dance. But she doesn’t make enough to pay for her family or her life. She has a fiancé who works in payroll but that still doesn’t help pay the bills. She’s afraid to leave because of the love of the game and the connections are family at her studio. It just seems she could be so much more than dance… and do more for her family and herself! Thoughts?