You might be the reasonable exception of someone trying to figure out why this might work for someone. A lot of other comments are framed in a way to belittle people who like this.I would not say there is a lot of passion on the subject. It does not take a whole lot of effort to have an opinion and post it on a forum. I would think a lot of people also do this for all sorts of things all the time, trying to understand the mindset of why someone would like or not like something. I would say it is more weird to be motivated by digital icons. Some participation ribbons might just help push people over the top!
As for why it works, I'd say it's something similar to a completionist mentality in video games. In some people, it just triggers a nice feeling to complete something on a check list. In actual terms, the Fitness awards algorithm tracks your progress and generally pushes you to do a little more than you did last month. So getting the award means you progressed without having to track and analyze every workout.