As an English teacher/trainee, I strongly agree that learning a target language is closely tied to learning of its culture. The issue of culture learning and teaching has been widely studied in the field of Second Language Learning and Teaching over recent years. So I believe it's impossible to learn a language without learning about its people, culture, and values.
It's a huge part of ENGLISH culture, not of the culture of the country the guy who asked the question come from. In Brazil, for example, it's not rude not to say thank you when you pay for something in a store. The best (and perhaps the hardest) part of learning a language is to understand not everyone thinks like you do
Agree with you , Teachers need some motivation too :) .
Best regards .