the reason was and always has been the same: you could defect on pragmatic and material grounds, but your family and all your life remain in the nation you left. So, specially for a young man, it’s often not an option.

You are a young german. You defect to the USSR. And then? your family hates you, your former country considers you a traitor, you don’t speak the language, don’t know the culture and everyone in the new country is at least suspicious of you.