At a guess, you probably have a
very large base of genealogists on there!
Old maps are incredibly useful for genealogy because it helps you do lots of stuff. Say someone lived on "House #3 Country Road" in (county), but County Road no longer exists, and all that can be found is a brief description of "County Road is now Main Street, Bank Avenue, and Church Road" It would serve as a vital clue as to where their ancestors house used to be (or may still be!)
It also helps to give a better narrative of how the community has expanded and changed over the years. Instead of just, "It was probably all forest land, then farm land, then suburbs or something?" Instead you can see stuff like if there were spikes/declines in populations in response to various events (gold rush, mining, factory work, railroads, war, highways bringing/diverting traffic, and so on). They can also show how the land may have changed from environmental factors (mud slides, earthquakes, tornadoes, and hurricanes). Maybe you're from a "Military family" but never knew why, only to find out that a Military Depot opened up 2 minutes from their house just as great-grandpa turned 18.
In a real sense, it describes not just the family and where they lived, but the type of place they knew, and community they grew up in. It hints at how they saw and experienced things over the years. "But why did great-great-grandpa insist on moving his entire family? He had lived in that beautiful house his entire life! Ah. They put the railroad 6 inches from his backdoor!"