Selfishness is part of the human condition. Tribes needed to fight over resources and mark their territory in order to keep the tribe alive. It’s in your instinct.

There have always been borders and territories, and there have always been fights and wars over it.

I don’t really see how your “if you don’t use it” policy applies here, and I also think the problem of this topic is easier than that.

Would you rather everyone can just walk into your house and take whatever they want? I for one am quite happy with the rules and morals we keep.

Those flags put up are often there to keep different cultures with different rules apart. It’s not as easy as erasing borders to have a free world. People are too selfish for that.

Sure, governments still steal all the time. Things are definitely not perfect, but that’s not related to someone stealing your lighter.