Some countries return tax to tourists in airports.

I don't understand it. Why is it happening? What was the logic behind the decision? Why is it only related to purchase tax and not to income tax? Why is it so important to preserve original packaging?

It is obviously a sort of segregation and nationalism. Why did people vote for it?

I have heard that European countries are doing it along with Japan, Australia, and maybe some other countries are doing it as well...