Whether it is necessary or not depends on the vitality of your soil's microbiome. If your soil is a microbiological party with a tonne of macrobiota coming over for the buffet, you have no need of anything.
If your soil isn't already a happening place, however, I suggest you look at some of the material available on this site. Bryant Redhawk has a couple of threads on soil that are really helpful.
One topic he deals with in detail is the creation and use of compost extracts. These are added after the soil has enough organic matter and has been amended to deal with any issues of drainage or nutrient or mineral insufficiency, not to mention pH.
I think that the inoculated nitrogen-fixing bacteria host crop seeds are inoculated because if you don't already have the bacteria in your soil, they won't just magically get there because you planted a nitrogen-fixing bacteria host. So in that way, in depleted soil, you are better off going the inoculated route.
But I think the best path is probably looking into making your soil as chock-full of life as you can. That will cover all bases.
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein