You've got to remember that CB is traditionally a short range radio service. While atmospheric conditions can greatly impact range, and those running much greater than legal power can get pretty far too, most of the users are only going to get a few miles at best.
Since the "average" user slaps in a cheap antenna that is rarely resonate, doesn't understand what a ground plane is, can't even spell SWR, and likely prefers "low profile" antennas, you really are looking at a few miles at the best.
Expecting to hear a lot of traffic on 1/40th of the channels at any given point in time in any given location is unrealistic.
I've driven all over the western US, and usually don't hear much traffic.
On major interstates in big cities, I've heard a bit of traffic. Usually truckers talking briefly. Occasional longer conversations.
Out in the middle of Colorado, I had a brief conversation with a couple in a moving truck for a few minutes, then range became an issue.
Sporadically, out of the blue, I've passed through areas where there's a lot of very localized traffic.
When the atmospheric conditions are right, I've heard traffic from all over.
Truth is, unless I was on my own, I kept the CB off. My wife and young son didn't need to hear some of the traffic on there. Just not appropriate for many people.
When "skip" is running, sometimes it just gets way too annoying to put up with. I can only stand to listen to some guy with crappy audio repeating the same thing over and over and over and over and over…..
CB is great if you are in need of a short range radio service and have someone specific to talk to.
It can be slightly more useful if you are willing to run more than the legal power.
Random contacts are bound by the limitations of the band, power and antenna, as well as the location, band conditions and wether or not someone else has their radio on.
As a tool for random/hobby type contacts, it's really dependent on the activity in your area.
What I've seen far too often is users will buy a fancy $150.00 radio, but then spend a whole $20.00 on a cheap magnetic mount antenna and expect it all to work like a $150 setup. People under estimate the importance of the antenna set up.