Because most people want to vote for someone belonging to either the Republican or Democratic party. They don't understand how these two political parties have become so screwed up that they cause this country so much trouble. So, they listen to the rich people - because THAT'S what gets your face in the spotlight, money. You don't stand a chance of winning a campaign if you don't have the political party backing you - and vote for which candidate they prefer. So, Obama is from the Democratic Party. He will not be a liaison between the 2 parties because he can't exclude his own preferences for his party. If the Republicans want something done the Democrats start bawling. If the Democrats want something the Republicans dig their heels in.
It's called compromise, people! Not all members of these political parties are this way but the majority are. The Tea Party Republicans scare me a little but that stupid b.s. with the Occupy movement for the liberals was even worse.
The president is a member of a single party rather than a liaison between all parties because of democracy. He is the representative of the people and should be self governing by appointing other members to act on his behalf.
Unfortunately, politics have become interwoven with hot button issues, like abortion, gay rights, religious beliefs. This forces politicians to pick sides rather than just simply representing ALL people, which is what they are supposed to do.
political parties were first avoided in America because of negative effect in earlier civilizations. HOwever we fell into the trap and now after less than 300 years as a nation and around 500 as a civilization including before we were apart from Great Britain, we are divided. Theis is not because we are openly different from each other but because we label ourselves and categorise based on personal beliefs instead of just agreeing to disagree and believing what we each individually believe in.