An interesting observation. I guess he appreciated that not everything changes at the same rate, or to the same degree. Since 1951 (when Empire was written) communications, for example, have advanced to a ludicrous degree with the development of smartphones and the internet, but we still travel around in very similar ways, farm in very similar ways, etc. So, by leaving a lot of the mundane as it is, he's reflecting the reality of how 'progress' takes place. Also, I think perhaps Simak was more interested in how humans would develop in the way they think, than in what they will invent. A third thought - its probably a useful literary approach to keep certain elements of a SF story familiar to keep the reader engaged.One of the most interesting things, I think, isn't what sort of new science or technology Simak created, but rather the mundane things he left in.