I think it is great that we live in a society where we can cohabit and where there is no stigma attached to having children without being married. However making the commitment to be with someone, sharing property, and committing to having children is viewed somehow in a romantic, rosy light - I love him/her, I trust him/her, he/she is my soulmate. That's lovely. But being together, financing your life in the short term and the longs term, dealing with the practicalities of day to day living, and having children should also be a hard-headed and logical look at how that might work out.
If, in the rosy glow of love and tenderness you can't discuss or compromise or reach agreement on who will pay for what, or if you can't share with your loving partner what your dreams and practical expectations are for the future, then how on earth are you going to do it when you're sleep deprived, relying on one wage, and potentially with vastly different responsibilities for earning and childcare?
I agree with the sentiment in this, and I think that part of 'entwining your roots' is about financial and legal entanglement (or at least the ability to discuss it and make joint agreements):
"Love is a temporary madness,
it erupts like volcanoes and then subsides.
And when it subsides you have to make a decision.
You have to work out whether your roots have so entwined together
that it is inconceivable that you should ever part.
Because this is what love is.
Love is not breathlessness,
it is not excitement, it is not the promulgation of eternal passion.
That is just being "in love" which any fool can do.
Love itself is what is left over when being in love has burned away,
and this is both an art and a fortunate accident.
Those that truly love, have roots that grow towards each other underground, and when all the pretty blossom have fallen from their branches, they find that they are one tree and not two."