Talk to very active CCR instructors. Up to 25% of the units end up on second hand market after the certification and 5-10 dives. Just check Facebook groups.
Reasons? From what I've heard it's quite simply "reality did not meet expectations".
Unit complexity in maintenance and during dive, lack of chances to use it in anger and keep current, availability of CCR teams/buddies, availability and cost of sofno/O2, availability of dive sites with enough depth/profile, lots of interesting ways to die (which combined with insufficiently frequent diving leads to problems), etc, etc, etc.
I personally know a VERY experienced diver, who dives every day and for a decade now ditched his CCR - in his words "I just can't be ar**d".
He's sometimes involved in body recovery, serious public safety missions - all on OC for the sake of simplicity.
Me and my wife - we're never going back to OC. But we have a CCR team (ourselves, another family member and a local active club), we love tinkering and keeping up to date and units in tip top shape (over an hour after each dive), we dive at least every second weekend and usually every weekend plus two-three CCR trips per year, etc, etc, etc.
CCR is a superior tool for a specific set of dive profiles and preferences. If you don't do those profiles and don't have those preferences - it's a tool looking for a problem to solve and ending on "CCR for sale, only 10 dives" advert.
Just my five cents.