President's and their Parties

Why is it that Presidents don't do what they believe in? They always try to appeal to their party and, it makes sense because in a general statement, the people did elect theirparty but more specifically they chose that person, the one and only President of the United States. It seems quite illogical and I would like to know what you guys believe. I personally think that they are afraid of the consequences of possibly going against some of their parties beliefs. I am not trying to dis the United States government as I do believe very strongly in it and I love this country.

P.S. I could go talking on and on about politics but I really don't feel like it. This is just a question that often bothers me when I do speak of politics.