You must be pretty naive to think that the "possible abuse hasn't materialized in Finland". First of all, this idea is also present in the German tax code ( 42 AO). It is a constant reason of judicial trouble, and it puts the state above the law - because it only works against the taxpayer and not in other circumstances. It is a clear indication of a cleptocratic government. Second, there are hidden costs: In your example, a couple marrying and then divorcing again is clearly f*cked. Their marriage is lost, and so is their money. And, of course, their belief in justice. Which is the greatest cost of all.
But I know, people with collectivist tendencies see the "state" or "society" as standing above individual justice.