Not all men, but you know that. Statistically, men are more likely to leave. You are right about that.
My ex did not leave the first time I had cancer. He cleaned up vomit, made me fresh juice, and took care of me.
However, after my mastectomy, he did leave. However, putting myself in his place - that year he lost his father, lost his mother, lost our cat, and then got me through a brutal mastectomy that had me dealing with a lot of pain. After I was mostly recovered, he couldn't deal with it.
The problem - men don't have the support networks women do.
When a woman is caring for her husband, she has friends who send her cards, call her up, offer to get groceries, etc. When a man is caring for his wife... all too often he doesn't have the emotional support he needs. If he is lucky, his wife's friends help out but while they may bring over meals, they don't give him emotional support.
Now, I am going through chemo again and in the treatment room, I am more likely to see a man alone than a woman. The woman will either have her husband with her, or a daughter, or a good female friend. I seldom see a woman alone, but, just today, in chemo, I saw three men alone.