As sulfur was removed from diesel, lubricity additives have been added prior to sale. They seem to meet the necessary standards.
Seems the concern for this by the big engine manufacturers is, if the fuel don't meet the standard, use an additive...if it does, there is no need to regularly add one.
So it would seem to me, without testing your fuel every fill up you are just guessing, I just havent convinced myself that burning several hundred gallons of substandard fuel every once and awhile will probably not hurt my engine to where I would ever know.
If I use it every time, then for the better, well known and proven additives, of which I don't consider MMO to be a member of, the cost is not great, but there. Also it is just having it on hand when travelling, and adding it at fill ups that is not a big deal, but still an added step. Again for something that is relatively unproven as necessary by any large body of science that I completely trust.
All I know is the vast majority of boaters and commercial operators I know DON'T use additives and don't seem to care and run their engines for as long as anyone else.