Lots of reasons, I have seen it since I was a kid in junior high, then me, my friends and family (my little brother) played the Gameboy games (Red, Blue, Yellow...). And then cause its simpley a good show (characters, plot, the imagine world of Pokemon etc). Heck, I study at university but still needs a buit of nostalgica from my childhood. :)
I have seen it in 3 dubbed versions, the Danish, Swedish and Italian, however I mainly look at the english version.