You want to know why?
Get into the insurance business and learn what
actuaries do.
The insurance company tells the carrier if they want to lower their risks, they need to have CDL holders in every vehicle that they have in the fleet.
Risks equal costs.
It is the idea that the training to get a CDL, which is above that of a monkey getting a driver's license, shows that the person has a little more knowledge of how a vehicle operates than that monkey.
I feel strongly that no matter what you drive, if you are working in a commercial transportation job like this, you should have a minimal amount of knowledge of things - including how to check the oil and change alight bulb.
I imagine that one day soon there will be another FMCSA change, that CDL holders of all sorts will have to earn Continuing Education Credits as part of maintaining the license.
It is like the other issue that vanners seem to poo poo, CSA.
The CSA has nothing to do with the vehicle but everything to do with the driver. So even though you don't have a CDL, you can accumulate points for the company and not yourself - per FMCSA.