Well I am not a member of the nvs but I used to be a member of the NDS (National Dahlia Society) and if the nvs is anything like the nds I can see where you are coming from but I would have to say you are quite wrong.
Although it is true they cater for the 'show grower' most of the members are just people like you and me who have given there time to the betterment of the Vegetable or in my case the Dahlia.
For instance when you go to a 'top show' and you see what these people have produced you may 'drool' and wonder how did they got them like this? well in most cases you only have to ask who is on duty, and they will gladly tell you.
They will point out types of plant to buy, literature to read and now that we have the internet, websites to go to.
I am also a member of the RHS and I know If I have a problem I can ask and within in a short space of time they supply me with their expert advice.
Oddly enough in a roundabout way some of the advice I give here at A4A is a result of getting information from societies such as these.
But I take your point perhaps these societies should try a bit more to get rid of this image.