Germany.
That rule prevents a lot of abuse of marriage laws (like “marrying” before a large windfall income to save taxes, then immediately “divorcing” again).
It gives couples time to fix their marriage if possible, before all of the legal ramifications take effect.
Or to separate their goods, get legal council, plan moving out, etc. if it isn’t fixable.
And the mandatory alimony payments allow the partner who cared for the household to leave their (possibly abusive) spouse without becoming destitute.
I wonder what makes you think it’s backwards?