How stay at home moms get their reference letter?

I really wonder how stay-at-home moms get reference letters when they restart, return to, or start their careers after staying at home for a long time (five years or longer).
I also wonder how stay-at-home moms obtain recommendation letters for graduate school after being at home for a long time—especially those over 40 who are going back to school. It may have been 20 years since they were in college, and they no longer have academic connections with their professors.