This is really odd, particularly considering that Turkey is by far one of the friendliest places I've been in my many travels (well, at least many travels when I was younger).
I question whether they're aware of the grief that their reviews are causing. In any case, it's still pretty inconsiderate to tell someone (numerically) that you think their work sucks, even if you don't really mean any harm.
All in all, probably an extension of the whole "cursing/attacking/belittling someone on the Internet doesn't count" phenomenon.
They don't think that they are hurting developers, firms, etc. I saw a comment like this: "Hey dude, don't get me wrong I loved your app, it is really fun thank you; but I am giving 1-star just to be seen".
I guess they don't comprehend stars' purpose. When they are searching apps, they just scroll down to the comments. Stars are not a way to judge the apps. Also, with the Google+ integration, they enjoy their full name is being seen on an app's page. Weird.
Turks are friendly in person, and warm and welcoming. But in general, they don't seem to have as much of a general concept of civic duty. Eg they just litter, because there's no visible victim, and they don't see the guy who has to pick up the trash.
I question whether they're aware of the grief that their reviews are causing. In any case, it's still pretty inconsiderate to tell someone (numerically) that you think their work sucks, even if you don't really mean any harm.
All in all, probably an extension of the whole "cursing/attacking/belittling someone on the Internet doesn't count" phenomenon.