I have the same issue with my '57 Hercules 3-spd. It fits me very well, works great for a go to the store / bank / Post Office kind of errand bike. And, it really isn't worth much (if anything) on the used bike market. So, since I have the room, I keep it.
I've had it since '82 and it was actually given to me by a bike shop. It was brought to the shop for repair but then the owner passed away and the owners wife didn't want it. The cool thing is, it came with a CTC (Cyclists Touring Club) badge from England. I have ridden it on the Lake Pepin 3-Speed tour but really, it doesn't get much use.
I did pay to have it shipped from St. Louis to Santa Ana when I moved to CA in '95, so I guess that says something!
Rick / OCRR