You mean the fathers who are driven out of the family by mothers because their existence, other than in the form of cheques, is an inconvenience for the woman? The fathers who eventually give up and go away because the courts simply won't punish mothers who play games with access and practice parental alienation? Those single mothers?
And of course many mothers are single because they choose to bring a child into the world without the benefit of a financially and fiscally stable relationship. Those single mothers?
In Canada women initiate approx 3/4 of divorces, because they are "dissatisfied" what role does that play in the large number of single mothers?
And then of course there are the mothers who are single because they don't want the father hanging around and being an interference, so they simply never tell the fathers that they are pregnant or that he is a father.