LJs got it.
The small G-loads allowed the standing position. This was a brilliant idea that allowed the astronauts to position their heads close to the front of the LM, which meant that quite small triangular windows would give wide visibility. This saved an enormous amount of weight compared to earlier sit-down concepts that had very large expanses of window to get the same field of view (windows for space use are very heavy compared to the surrounding structure). Note the concept on the left below. I have seen designs that had even bigger windows.