My rationale for buying grafts is:
1. I am in Michigan’s elk range. I want vigorous trees that will grow out of their reach, and as rapidly as possible.
2. We also have bears. I hope to have trees that will someday be large enough to so that bears do not totally destroy them.
3. If voles, mice or rabbits girdle my trees I want a chance that root sprouts might be from the scion variety.
4. I hope for trees that will endure for generations, and I have several seedling trees that I believe are at least 80 years old, and perhaps much older than that.
Unfortunately, many of the trees that I see are simply grafted too high to make burying the grafts practical.
My first two reasons are less important with trees produced on full-sized RS, like those from Blue Hills. But trees from big box & farm stores that I’ve seen are often on unknown RS. I have no use for trees on dwarfing RS, except as scion donors.
I’ve been planting apples & crabs this way for 35 years when the grafts are low enough, and it has worked for me. But I have extremely light, sandy soils. Perhaps it would be less successful in heavier soils or in clay, I do not know.
I am not saying that burying grafts is right for everyone. But in my situation I believe that the benefits outweigh the disadvantages.