Interesting question...I look at it from a historic preservation standpoint. Neighborhood gas stations are disappearing rapidly, and it's important that people remember the times of abundance.
I don't think road map collecting is as visual a hobby. It's hard to display them in an eye-catching manner like you can with globes and pumps. But IMO, tracing highway routes and travelling the back roads using historical road maps is a heckuva lot of fun.
Personally, I do have an eye toward protecting my investment. It would be nice if someone recognized the value of my collection when it's time for the retirement home. I try to document my maps and postcards as well as I can just in case their final home becomes an archive instead of a collector's home, because to me, history is part of value.
