One of the reasons historical fiction is so popular is that it can take a reader back to times that were very different, and hence very appealing.
Go back 20 years and there's virtually no Internet. Thirty years, home computers were still not common. Forty years, little cable TV. And so on. You have to go back well over 50 years to get rid of TV, though.
Do you see where this is going? Change has come so fast and is so deeply ingrained that now, historical fiction can take place in our own lifetimes.
It's a scary thought, but someone from the era of the Civil War could go to the 1940 or 50s without too much trouble. The technological triumphs of the mid-20th century have their roots in the 19th century.
But now things are really different - we grew up in it, so we've acclimated to the changes. But our Civil War visitor would be sorely perplexed in a world in which she was truly alien.
Now...we think differently. We are alone more, but far less self-reliant. We have more laws, and more crime. We have more religion, but less faith.
And so goes our visitor, back to her quaintly inefficient world - happily, without a backward glance toward those of us left behind, in the future.