@VeroniqueB99 How is the parent who stayed the problem?
- Maybe she didn't want him to stay.
- Maybe she replaced him with someone who didn't want to stay.
- Maybe she doesn't know who it is.
There can be a million reasons. Sometimes its him to blame, somtimes her, somtimes nobody. 1000 cases mean 1000 different situations. But simplify it by blaming the gender (or race, religion, etc...) I don't like is something I'd usually expect from people who are politically far right.

@ausm I think the point made isn't about who is responsible for the situation, but rather about the its description. We say single mother but we say it because of the absent father. Why he left is another thing.
I don't entirely agree though.
@VeroniqueB99