why are the germans considered humorless?

This (whole article here) seems like an insightful paragraph:

I think that the British prejudice about Germany’s supposed humour famine stems from the fact that there is no German tradition of daily banter. In London you can hear a dozen wisecracks in a day — at work or on the bus or in the coffee shop. They may be lame, but at least they’re quick. In Germany, humour is stockaded, kept apart from everyday life. In the evenings Harald Schmidt, a genuinely funny talk-show host, will crack their sides. But only after dinner has been eaten, the plates rinsed and the yoghurt pots washed, ready for recycling. In the office next day people will repeat Schmidt’s gags and they will laugh again. However, they will fail to spot the inherent absurdities of their own office life.