Why do men behave differently?

Why do men behave differently when the couples are alone and when they are in front of anyone else, especially the guys' mother?
Why can't they handle many things in a polite and more nicer way? Husbands promise that they will not behave differently in front of his mother but then they continue to do so everyday.
why do men don't understand that the lady behind is actually telling something only for his good? if he feels that whatever he says is achievable, but contradicts his wife's thought, then he can tell it in a more nicer way and listen to her side of argument as well.
Men are men and there is no cure or solution to this problem.