I suspect that 'monetary advantage' does sometimes enter also into 'marriage commitment' as well as to living together without 'marriage' commitment.

Actual life is often 'messy'. People sometimes need to do the best they can in the circumstances of their life. Hopefully 'the Church' can walk with them and help them along the way.

Strangely enough, sometimes it is our well-meaning 'rules' that set up a situation that causes the opposite of what is intended. 

Case in point: A man once came to arrange for baptism of the couple's 6th child. Upon enquiry, it turned out they never were 'married in the Church'.
Reason given was: 'Oh, Father, to get married in the Church is something SERIOUS! Before you do that, you want to be SURE!!

Presumably a 'good Catholic family', probably receiving Communion, or they would not have come to get their children baptized.

People take the 'rules' and develop their own reasoning. How best to work with them to achieve growth is the question.