This is not facebook....
Why does everyone post about stuff that has nothing to do with what this app is about?
because even though this app is about working out its still a networking app
Forums in most any internet community have an "off-topic" section. These forums are a little weird in how the interface is presented in the app... So these topics appear mixed in with all the others, but there are actually forum sections here, like all other forums. (diet and nutrition, teens, weight loss, etc.) They just don't show up by default organized on a forum home page like most other forums, here you gotta look for that page.
I assume it's to met and make friends with people with similar interests. For one, we all workout! :) and many if us are trying eat to well too. This is a major part of our lives and effects us everyday. Why not make some friends while we're at it with some "off" topics?