I wont argue that ideally we want to get the complete nutrient from food sources. However due to the rapid change in society and toxin exposure we now face its simply not practical or even possible to get everything we need from food, especially since our soils are so depleted due to over farming etc.
Yes, I have read the founder of vit C could not cure scurvy with ascorbic acid however that was like 90 years ago.
There are actually multiple forms of ascorbic acid, some worthwhile and some worthless. It very well could be the early founders version of ascorbic acid was not effective but today the manufacturing process has been greatly improved and if you spend some time reading case studies and such on medline (who by the way intentionally withold about 40 years worth of orthomolecular journal entries) you will many cases of scurvy are cured with ascorbic acid.
At the end of the day we have to look beyond nutrients as just simply nutrients because in essence they are. They are electron donors and anything that depletes electrons will also deplete the body of nutrients. With that in mind pathogens and toxins use up electrons at an alarming rate, so fat in fact that they can cause nutrient deficiencies that are nearly impossible to recover from with food alone.
Ascorbic acid is an extremely powerful electron donor and the fact its basically non toxic makes it a great medium for imbuing our bodies with the electrons it needs to control pathogens, toxins and free radicals..