I'm surprised that more people don't let kids "practice" manners at home. It just makes going out less stressful if they know what is expected.
And manners aren't just for "company" or "public" consumption--they should be part of their daily family life. Goodness knows that I've done my share of "get your elbows off the table" and "please use your fork THIS way" and "don't take such big bites" but it's nice to have kids who know how to act in public.