The reason is very simple. Does not exist and can not exist universal, mandatory standards for everyone humor. All people are different. Everyone has their own habits, temperament, hobbies, personality, due to different hormone levels, and especially the resulting education. Everyone has their own personal idea of what is considered acceptable, ridiculous, and to what extent. Of course, a huge role in this is the mentality inherent in a particular people, its customs, traditions, lifestyles and living conditions. All this forms the relation of man to the ridiculous, to put it in the form unique to him a sense of humor.
Finally, we must not forget this fact: the idea of what is considered funny with time changing rapidly. Not accidentally, in the preface to the Russian edition of the famous English humorist JK Jerome "Three Men in a Boat" said: "We know how rapidly aging laughter. Often what was previously caused loud laughter, and now will not cause even a smile. " Neither this be one of the reasons the notorious problem of conflict of generations? All this taken together well explain why a sense of humor in different people is also different. Different and can not be.