

I keep a CB radio in my car, and have a few friends with them
It is actually really handy when you’re road tripping together in different cars to be able to just grab the mic and say something to the other vehicle when you need to stop for a bathroom break or you’re having an issue with your car or want to give them a heads-up about whatever.
If you’re fairly close together a set of cheap FRS walkie-talkies from Walmart does the job just as well. Probably worth stepping up to CB if you expect to lose sight of the other vehicle though, range is usually a bit better.
It’s especially handy if, like me, you go camping and such in rural areas with unreliable cell coverage.
You do occasionally also get helpful heads-ups from truckers if you’re listening to channel 19 about road conditions, police activity, traffic, etc. but mostly it’s just idiots babbling about conspiracy theories and immature bullshit.

Because they’re fucking everywhere, something like 90% of the US population lives within 10 miles of one.
It’s basically shorthand for “this is a common and readily available thing that you can acquire anywhere in the country for cheap even if megacorps have driven all of the local specialty retailers out of business in your areas”
As opposed to something like a HF ham radio which is a specialty item that no big retailers like walmart, to the best of my knowledge, carry, and so you’re probably not going to be able to find it locally.