The reason for a single choice pole:
I just bought the Canon EF 40mm f/2.8 STM pancake prime with the intention of using it on my Rebel T4i and carrying it around like a point-and-shoot. I just sold my Canon G12 and used those funds to purchase the 40mm. However, I'm still more comfortable with my kit lens, EF-S 18-135mm f/3.5-5.6 IS STM; I've shot most of my best photographs with it. But, I wanted the 40mm pancake prime to push myself, to bring back those old 35mm film experience w/55mm, to zoom with my feet. (Note: 40mm on a crop sensor is a 64mm for 35mm full-frame equivalent). So, I intentionally want the pole to be single-choice. If you had to grab just one lens and go, which would you be most comfortable with? It's a hypothetical situation. I chose my kit lens with all its distortion and chromatic aberrations issues in the pole; I hope one day that will change to the 40mm; it's a better lens in many ways.
In a way, I added the pancake prime to answer the question to the vast body of knowledge of TPF what they would recommend in that one-lens hypothetical situation.
In reality, I own four lenses (check my profile) and they all fit in my little SlingShot 202AW, which is a small camera bag. When I'm intentionally going to a photo shoot, there's no reason for me not to grab that bag and give me every option.
Today, it's between the old reliable kit lens and the new 40mm, and I have to give the latter a chance.