Why Windows 8 Upgrade is not available worldwide?

I am from Bangladesh, here, 99% of the PC users happily and without any hesitation or issue run pirated copies of windows. Nobody even considers paying for windows when they can get it for free. I was excited while windows 8 upgrade pricing was revealed and I decided to upgrade to windows 8 legally [ my current version of windows is also genuine ]. Today I finally managed to get the money for upgrading and downloaded the upgrade assistant, everything was going smoothly the compatibility report and staff, I clicked next..... ERROR!!!!! "Sorry, windows 8 is not available for online purchase in the country/region you're in".Okay, tried to purchase the DVD instead, guess what it wont be shipped. What are my potions now, wait for the retail version to be released and pay a 100$ extra. This is for a country where every PC runs pirated windows, what massage are you sending Mirosoft.