I would say it is a consensus among people who have used non-staggered layouts for a sustained period - the benefits are definitely noticeable to someone with RSI too.
People are satisfied with their keyboard layout because it's good enough for them, and they've not experienced using other layouts enough to compare the benefits. It's very much like PGs "blub paradox", in which the a typist becomes familiar enough with his keyboard that other, allegedly better keyboards seem like only minor improvements - not worth the effort to switch. For most people, this is probably the case - it's only if you're typing for several hours a day that there will be tangible benefits to hand-optimized layouts.
