Unfortunately, Jack, you are simply wrong.
Deer crave the salt for osmonic balance in their blood. That alone is a benefit provided to wild deer. There is no argument against this simple fact. WHEN THE BALANCE IS OPTIMAL DEER DON'T CRAVE SALT.
Another study was done on selenium in an area lacking in this mineral. An artificial source of this mineral was found to increase the blood levels of local animals, including deer, to normal levels.
It is also well known that crops meant for human use, corn and beans and others, often deplete the local soils of needed minerals. Animals in the wild that eat these crops have been found to lack certain minerals (along with the domestic animals and humans). Supplementation helps to correct the problems (one of the same reasons we supplement domestic animals). While in the U.S. we are FAR behind in our attention to this mineral depletion, other areas of the world have been studying it for some time and actually actively return minerals to their farmed soils, in itself a form of supplementation. Areas of low magnesium, for instance, are well documented.
Will deer fall over dead without help? Nope, even without 100% of their optimum mineral intake. Will supplementation help? Yes. In areas where certain minerals are lacking, supplementation has been found to work on several species of animals.
Yes, there are a few areas in the US where the soil is lacking in selenium, and too much selenium can be toxic. Yes, some farming techniques can deplete soils of certain trace minerals, yet free ranging deer populations have a high percentage of native foods in their diets and are not lacking in minerals.
Does the free ranging deer herd benefit from minerals? Absolutely. They will die without them. Do they benefit from mineral supplements? There are absolutely no peer review studies available in the scientific literature to support any such claim. If you believe there are such studies, please cite them for us. My mind is always open to be changed with sufficient empirical evidence. That is what science is.
Extrapolating "scientific" claims beyond the evidence is one definition of Marketing. There is noting wrong with marketing as long as it is clear that it is marketing. I'm glad to see the signature line with the link to your web site selling mineral supplements. This is a great way to both market your product and for readers of this thread to evaluate your claims.
This is a habitat and foot plot forum. Most of us doing such work have limited resources. The key is determining what the limiting factors are for the local deer herd and applying limited resources wisely and efficiently. The best way to do that is to assess the home range of a deer and find out what key components are missing and which ones are limiting the herd. Quality Deer Management is often described as figuring out the lowest hole in the bucket and plugging that first before moving to holes higher in the bucket. I realize not everyone on this forum is doing QDM; some are looking for simple attraction.
My point is simple. With limited resources, whether one is doing QDM or simple attraction, using methods with a clear scientific basis and no extrapolation beyond the evidence when matched with ones goals are the best course of action. If food plotters want to ensure their deer get sufficient minerals, the best course of action is to do proper soil sampling and properly fertilize fields and avoid planting monocultures or rotate crops to avoid trace mineral depletion. Money spent this way does double duty. Not only are plants the most efficient mineral delivery system, they also deliver high quality protein and carbs that do benefit deer. For those interested in attraction alone, they must weigh the potential consequences in disease transmission for using point source attractants verses using food plots that allow deer to naturally distribute for feeding. If they choose to go with a point source lick, the most efficient way is simply to use salt. If one wants to go on faith that minerals will help their deer in some way, the most efficient way is to simply add some low cost dical and trace minerals from the local coop versed BOB mineral supplements.
One nice thing about a QDM program is that it collects empirical data and analyzes it to help managers make good decisions about whether their programs are achieving the desired goals. A couple common measurements include antler size and yearling weights. Are there any studies that show mineral supplements improve any of these metrics in a free ranging deer herd? Nope.