Cheating on people is harmful too. It often results in broken homes and marriages, which is harmful to children's development and well-being. So by that logic,

Cheating on people is harmful too. It often results in broken homes and marriages, which is harmful to children's development and well-being. So by that logic, cheating should be illegal too. By the way, society hasn't decided anything because it's not a sentient being. The politicians running our governments have decided that punishing people for "tax fraud" is a great idea, mostly because they don't want people to stop paying taxes.. which everyone would do right away if there was no punishment for disobedience.