In many countries, if you move outside, even for more than 6 months, you are still considered resident (and also required to pay taxes) under certain conditions.
For example, you might still pay taxes if you have personal interests in you country of origin, like if you own property or if you significant other and children still live there.
It is different from country to country. In my case, I am expat from European country living in the middle east more than 5 years already, and I would still have to pay income tax back home in case i owned any property there. I don't, BTW. :/