I was a lurker for years, and I've been a member for only a couple years. Was recently having a conversation with some fellow mediocre climbers, and here are some thoughts:
1) User experience: the forums need responsive design to handle mobile and tablet viewing. A mobile app isn't necessary if the site design is responsive, and most people won't use a mobile app. Need to migrate from UBB sooner rather than later to stem the death of the site. Main landing page of the site is great with new redesign, but needs the same applied to the forums.
2) Insider club. Spray overflowing into reasonable conversations, perception of getting criticized for asking questions or posting lame TRs of simple climbs. Old boys club.
3) "Competitors" have a few advantages, whether its: more general scope, better user experience, more welcoming to noobs, wider reach, etc: summitpost.org, mountainproject.com, TGR (not noob friendly though), nwhikers.net (more friendly/inviting environment), not to mention blogs, social media, etc. I might even get criticized for suggesting these places are better in some regards, which would just reaffirm #2.
I like CC and will still visit here occasionally, but I think the above are valid reasons.