I don't think most people put that much thought into it. It's not a psychological process. If they ask, just say you switched to a modern tire for convenience, price and better ride. I've traveled with a lot of people who had 16's, and the only comments I've ever heard were "Oh, that car as different size rims and this one". and then the owner says "yeah, these rims are off of a '35 instead of a Model A. They ride better, so I switched". And the person questioning doesn't really care. People were switching to different style rims and 16's in the era..... so i don't think they make a car look "modern".
I like the look of 19's better, but Im putting 16's on this week so I don't have to deal with those crappy tubes anymore. Plus, my 19's were almost worn out anyways. I do a lot of bigger trips, so it's also a piece of mind to know that if I have a blow out, or something tire related- I can just get to the next town and they'll have a tire that'll work.