No no... Often there's no such a need... 
But like Yun has mentioned, sometimes they just don't know how to
react to it...
People's reaction to such request can really be quite subjective...
Then again, sometimes when you think that you have not done
anything to irritate them, you also can't be too sure? Something
which might seems 'nothing' to you might really be 'something' to
some people? 