Why do people tend to consider Germans distant and unfriendly?

I have lived both in England and in Germany as an immigrant and I feel that the Germans tend to be nicer than the English. On a superficial level English people appear to be more friendly and open, but the feeling I get from them is that it's just a mask of politeness and they couldn't care less about you. Germans appear distant, unfriendly and upfront but I could connect with them on the deeper level. Also, the society is not as class divided so people from different social classes are more similar to each other. In England, people from different classes are sometimes almost different species.

Why do people tend to consider Germans distant and unfriendly?
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