It's a behavioral shibboleth. They don't hike for pleasure or genuine reasons. They hike so that they can post a picture on Instagram. It's just a thing you do as part of the bland, petty, superficial, materialistic upper middle class bubble.
As someone with family members who immensely enjoy hiking for non-status related reasons, I can confirm you are entirely incorrect. They started in a pre-Internet era and as far as I know, haven't changed their motivations since.
