6 Answers

Actually, for trucks that are working one particular job, they are very handy to keep updated. But also, a lot of times when you are pulling under a bin or silo to load different types of product, they direct you to move by radio, in order to spread the load in the body of the truck. They are actually used quite a lot in trucking, as you often have to park a distance away from where you load or unload...and that's also how they let you know to bring the truck up.
Truckers also look out for each other in letting an oncoming truck know about a cop sitting beside the road...otherwise a simple inattention going through multiple changing speed zones can cost you a day's pay.

yes back in the 1980's you did.....BREAKER BREAKER.....THATS A BIG 10-4 RUBBER DUCK!

yes, enthusiasts still use them, like with ham radios