A runner on first base with two out is much more dangerous compared to a runner of first having 0 or 1 out. The runner with two outs can move on any ball in play. The runner with two outs could potentially score a run on a bloop fly ball that lands for a base hit whereas they otherwise would have only got to second. They would have been tied to first base the whole time the ball was in the air in fear of getting caught in a double play.
There are a lot of advantages to having your back to the wall with nothing to lose.