I can attest to the fact the CB is indeed dying off in the trucking industry. There are many reasons for this.
1. Older generations of drivers retiring, in jail, drug rehab, or gone off to the sweet bye and bye. These were the CBers of yesteryear. I consider myself to be some of the last of that generation being a pre-CDL era driver since 1985 and my CB is always on even though my HF rig is used more but I'm always monitoring the CB.
2. Newer breed drivers have smart phones, laptops, Sat-radio, GPS, and other forms of entertainment and CB is the least of their desire especially since 1 on 1 communication skills are deteriorating due to the popularity of social media. You can say we all are going down this road to by wasting precious radio time logging on to this Forum.
3. Company trucks are governed, log books are electronic so no need to watch for smokey bear or know if the chicken coops are open. Also no need to say "break one nine for local info" because of GPS.
4. Not to sound racial here but the fact is many trucks on the road are driven by and owned by people from foreign countries like India and European countries. These are hardly the CB truck driving stereotypes of yesteryear. Lately there have been indictments of many of these drivers with illegally obtained CDL's from bogus driving schools and bribes from DMV officials to get licensed. Wonderful isn't it!
5. The truckstop lot-lizzards are even using social media and not the CB anymore to keep from being chased out by truckstop security. It's been a while since I heard " any of them at a truckstop say " break one nine, any drivers looking for commercial company".
6. The last reason for the decline of CB use is because if Fine-Tune radio shop can't be at all places at one time, it's not worth investing in a CB if it can be "Fine -Tuned" before you use it! 
