Because Republicans retained the US House. They have a mandate from the people. And they have the votes for impeachment, which is just a simple majority. The impeachment is equivalent to an indictment. The US Senate determines if the impeached individual should be removed from public office. Now removing him from office is near impossible, but we all need to know if crimes were committed. We have a right as US citizens to know exactly what our President is doing on our behalf. He is using our equipment, our money and our people.
They certainly have the votes to do it, but Bonehead and Cantor will be too
busy screwing us with another Grand Bargain and Amnesty.
I doubt we could ever get zero thrown out office. But what we can do is get Senate liberals to vote to keep him "in" office. A vote they will regret one day.