Hi Cactus Flower,
Back in the 'old days' marriage was the only 'respectable' way to have children. And having children/workers of tomorrow, deserved advantages.
Being 'married' does provide a public good, usually folks live a longer & happier life, unless they kill each other ;))
Our tax base has different rates for singles, married, married with 'dependents', married & filing separate, etc.
As an aside, our Pope Francis, prior to his new role, condemned priests in his country for NOT baptizing children born out of wedlock.

DO SOMETHING!