Why don't people with cancer go to work?

Right after my dad found out that my stepmom has cancer, she stopped working all of the sudden. She is a middle-age woman. However, both of her daughters (both in their early 20s) do work full-time. Even as though I was diagnosed with SEVERE autism, I am around both of her daughters' age and work part-time under the table at a small shop. Even my dad works and he had undergone some financial troubles for years.

Updates
1 y
My stepmom chooses to just watch TV and hang out with my dad pretty much all day.
Why don't people with cancer go to work?
Post Opinion