I don't think there are benefits to having untuned (do you mean not waxed), unsharpened skis. I do think that for some folks it doesn't matter. Do you need sharp edges if you don't use them? Do you need waxed skis if all you do is try to shave speed? Do you need well tuned skis to slide over a metal rail in the terrain park?
There are times a tune doesn't matter. There are times it does. I can't think of anytime a good tune would impede performance but lack of one will. There are tunes that might not be appropriate for what you are doing (i.e. SL Race tune on terrian park skis). I don't usually go more than 2 days without tuning. Not so much because I'll notice the difference, but if I do have issues, I'll know I can't blame the tune. There is no benefit to the longevity of a ski to not tune (unless you sharpen with a file obsessively).
My wife is learning to ski this year (first time ever and no I'm not teaching her). The best tune for her would help her go slow . She will probably spend the year in a wedge wishing she wasn't going so fast. Her skis will be flat on the base and will get waxed as required. The edges will be burr free.
To me, not waxing is like not putting oil in your car engine. Not sharpening edges is like not keeping your tires inflated to the correct pressure. I can still drive on the highway with low tire pressure, but I get better gas milage and will be safer if the tire pressure is correct.
Besides all that, how do you regulate "untuned" and how do you get the same performance each time from not tuning?