Why do so many people with "British accents" sound so snooty? (many, not most, but just many)?

I live in the USA and whenever I hear a British accent , I noticed it sounds just so snooty often times, and was wondering do British people know how snooty their accent sounds or why not?
Update: oh, and "pretentious"... like there is a "am I better /classier, more upper class than you ? contest" going on over there? how true?
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