Largely because the Congress is controlled by Republicans who put party loyalty above doing their job or basic decency.
Also, though, the VP is a crusading evangelical and possibly even more dangerous.
Also to the rest of the world, we are very sorry and most of us voted against him.

because he will never be removed from office by the senate. thats the reason. so all it does is make his base of dumbasses think this signals "He's doing nothing wrong!" and it strengthens their resolve. how impeachment works is generally not understood by most of the american people and they vote on how THEY think they are doing. they're being told that they're doing better and they believe it. it's not until they really feel negatively impacted that they will even begin to consider the error and even then they will sacrifice to meet the needs of their backwater conservative beliefs. so until we have a very solid mandate from the people it's a tough road. we need to beat them at the ballot box.