Al, do you only hunt in broad daylight, not bothering with the "temperature transition" times?
I have, in fact, experienced fogging due to temperature change, even with "purged" optics and have seen the utility, under proper conditions of moisture, of Rainguard treated (not addressed here, really, but just thought I would throw it in for fun) lenses. There is also a decrease in corrosion of internal parts (at least those not made of plastic) in purged scopes (however, that is only a problem over LONG periods of time...generally). They all have a use. The big point is the differential between argon/krypton purged scopes vs nitrogen purged. For most common usages, there is no utility to noble gases over nitrogen, other than perhaps an extended period of corrosion protection. That all assumes that seals remain intact and the gas remains in the scope body. However, seepage can be corrected. There are places which will "repurge" a depleted scope and refurbish seals. Is it a marketing device... of course it is. Is it, in fact, useful... depends. I only have a couple of scopes I've kept long enough for it to be an issue. In one, there is a noticeable degradation of visual quality with a tendency for fogging in fairly rapid temperature change conditions, and I KNOW it has leaked. The other appears to be maintaining integrity and is as clear and unaffected by the external atmosphere as I can expect. I may actually try to get it checked and repurged/resealed at some time.
Of course, I know people who have hunted for many years with one scope and never experienced fogging, as you have not. That does, however, not mean others have not experienced the converse.