I've answered this question several times over the years with an example of what happened to us when the rear tires weren't balanced. We had about 50,000 miles on our 01 Adventurer and with an upcoming trip to Alaska I didn't want to take the chance we would have tire troubles. I went to the local Wingfoot (Goodyear Commercial Tire Dealer) and purchased 4 G670 tires. I asked at that time to have them balanced. They replied they would balance them with Equal Powder. Since I had the powder in the steer tires and it was working well I agreed.
When I picked up the motorhome there was no charge for balancing on the bill so I asked if it had been done. The service writer replied that the technician must have forgotten to add it to the bill so he did.
When the tires were new all seemed well. As they started to wear there seemed to be some vibration problems. Fast forward 2 years and almost 25,000 miles and the vibration became an issue. We stopped at a tire dealer in Florida and asked to have the powder removed and balanced with external weights.
I was called back to the service area to find the original dealer had never added the balance powder to the tires. Now 25,000 miles later the tires had flat spots.
It took over 12 oz. to balance the worst one and the others took between 8 and 10 oz. Even then there was a pronounced vibration from the flat spots. I ended up replacing the tires with less than 35,000 miles on them because they had not been balanced when they were new. Tires that should have lasted 60,000+ miles went only about half the distance they should have. At nearly $500.00 per tire that's $2,000.00 We wouldn't have had to spend had they been balanced as requested.