Maybe, because if the government stops everyone from paying ransoms, there is no point demanding a ransom. The person whose wife is being held as a hostage probably won't see it that way.
The government does not hover a drone with you at all times that counts your cash and stops you. But are two sides to every transaction. if transaction breaks the law any side can go to the law enforcement. Depending on country they may get a bonus for this too.
Now please picture me how your wife's kidnapper goes to the police saying that the ransom you paid exceeded $10k.
Someone who did a much more serious crime is not gonna go to law enforcement because his ass is going to be the one charged considering the circumstances.
But if a massive cash transaction is illegal good luck kidnapper doing stuff with a bulk of ransom money. Hey it may even put him off that whole kidnapping idea yeah? Or at least get him caught so he doesn't kidnap more people somewhere else
Here in New Zealand there are maximum limits on the number of coins you can use so paying your tax with a truckload of 10¢ coins is illegal, but if you use $100 notes you can use as many as you like.
in Russia max limit is 1k EUR equivalent https://base.garant.ru/58074419/#:~:text=%D0%9F%D1%80%D0%B5%...).
apparently in NZ 10k limit is only for some transactions https://www.dia.govt.nz/AML-CFT-High-value-dealers-Prohibite... hope you didn't pay in cash more than that for a boat recently;)