I'll try to keep it short, but that won't be easy.
You are both "part right" to some degree, but also WRONG about a few things. The reality is much more significant.
Yes, it is a huge (valuable) public image boost. Yes, most are unaware of it's existence. But, while the cost is significant, the RETURN is far greater, and goes way beyond the above factors.
1st and foremost, it is an effective SAFETY PROGRAM. It also provides incentive to become better, more knowledgeable, professional Drivers. In the process, is provides a chance to show the industry in a positive light.
SAFETY: For those who participate, the rewards are significant -
both on a personal level, and for the Company.
The 1st requirement is to have NO ACCIDENTS for the prior year. NOT just preventable, or at fault. NONE, unless legally parked/stopped. That alone makes
those who take it seriously, drive very carefully. Thousands of drivers participate (and/or want to) each year.
The incentive to avoid any and all accidents is what makes the return on investment so huge. How many accidents need prevented in order to make it cost effective?
Average cost per Truck Accident - $148,279
https://www.cashort.com/blog/transportation-how-much-does-a-truck-accident-cost
"A recent article in the Business Report stated that if you take the average cost per truck accident, which is $148,279, as provided by the Federal Motor Carrier Safety Administration, it would take additional revenue of $7,413,950 to pay the costs of the accident, assuming an average profit margin of 2%. The amount of revenue required to pay for the costs varies inversely to the profit margin. Further, the cost of a truck accident with a fatality is considerably higher at $7,633,600."
Here's more, but based on 2005 dollars.
https://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/UnitCostsTruck Crashes2007.pdf
So, Safety is more than just a moral "feel good" narrative. Safety is also a cost saving necessity.
We could go deeper into the benefits (for the individual & the Company). Improved relationship with law enforcement, opportunity to see the "Best" side of the Company, knowledge that puts one in a much stronger position when dealing with leadership and/or law enforcement etc.. Just to name a few.