Benefits of grafted root stock (fruit trees)

Other than keeping a fruit tree “small” by reducing vigor, what are the benefits of grafting fruit trees to a foreign root stock?

I personally would rather have a vigorous tree and control the growth with strategic and aggressive pruning. Also, I just recently found out that grafted fruit trees (semi dwarf and dwarf) have a shorter lifespan than their standard counterparts. I’m in this for the long haul and definitely don’t want to be ripping up trees every 15-18 years. I don’t understand why decreasing vigor would ever be considered a good thing as it inevitably shortens the trees lifespan.

I’m asking this question for future reference. I plan to air layer some of my grafted fruit trees this year, potting soon after, and then direct planting in the fall; no grafting to a root stock though.

It just makes sense to me that tree growing on its on roots will do better over the long run. Those with lots of experience, what am I missing?