Happy you asked...to start, I own a 2009 F250 with camper package and just bought a set of tires from Discount tire. Not only was the balancing refused on this set but it's been many years since I've had any balanced.
1. Because of the quality of tires being manufactured today, unless you own a Porsche 911 or a like vehicle it for the most part isn't needed on most vehicles. Especially so the larger the vehicle becomes. Now a disclaimer...for anyone intent on buying the absolute cheapest tire they can find then balancing may be needed.
2. Revolutions of the tire wheel combination. If at normal highway speeds 35 to 65 on average the revolutions aren't high enough to create a issue.
3. Unsprung weight...wheel and tire are part of a vehicles unsprung weight. To use my truck as a example the tire and wheel weight are about 75 lbs. That alone is enough to negate any unbalanced condition that could come from the tire or wheel. And I use steel wheels, no alloy, because they work better with radial tires. More can be given on that if needed.
4. Suspension...today's suspensions are more in tune with overall design than ever, even frame twist is part of that equation. From reason 1 thru 6 all are connected. Especially so the way vehicles are sprung. On mine the front is sprung so well the OE shocks may never be replaced.
5. Weight placement. Most conventional way of balancing is with wheel weights, tape or clip. The size/amount have been coming down for years, this again because of the quality of the tires being produced. So where are they placed...too close to the center too matter. Same goes for the Centramatics.
As for Equal or other like products the need is so small it's too much of a risk allowing them inside your tires. I've tested them and found no appreciable damage to the liners. However given that the liners used in tires today are not as robust as they once we're and knowing that they probably aren't needed anyway why push it.
6. This is not a opinion, I've spent many years, too much money and resources, along with giving this advice and giving up additional revenues as a result. But the relationship with the customer made it worth the effort.
Again you have to consider each point made and the fact that when tied together the result is convincing. By the way as a consultant I used to charge for this, to you it's free.