Not only is it a matter of keeping the bar close to us (which promotes better balance) it is also a matter of minimizing the distance the bar has to travel (aka bar displacement). We all know that the quickest way from one point to another is a straight line. With that in mind, we are more efficient if the barbell travels the shortest distance possible from start to finish. Let's take the Snatch, the bar path on the left is a huge S-curve which is a waste of time and energy. The bar path on the right has less of a curve -everyone creates 'some' curvature, it is impossible to be straight up and down, we just need to minimize it. If you were to take both paths, straighten them both out, then measure them... You would see they were not the same length. The one on the right would be much shorter. That means it didn’t travel as far, making us more efficient lifters. Creating too large of a curve adds length and time to the bar path...not good!