Great question. It is similar to why do men have children with women and then walk out without a backwards glance. I think the reason is because raising someone else's children is a huge responsibility for some men. It is scary for the man and for the children. It can also be a life altering decision for everyone involved depending on the circumstances. Its not an easy situation because there are babies involved and it is a lot of pressure. Its not always fear. Maybe they just do not want children at all.