There is a certain romance to any
sufficiently outdated technology.
Clockwork has a
visceralness to it. It is hopelessly
analogue in a
digital world. It is
obsolete excellence. The idea that
Charles Babbage's
difference engine really could perform along side a modern
Cray supercomputer is strangely sexy.
What makes the steampunk genre so seductive is that an old, seemingly useless, notion can be important and interesting and fun. Since our mortal coils only get some hundred years, and our progeny only take half our DNA, it is through the meme alone that a person can influence the world after death (aside from your personal favorite flavor of afterlife, if it allows mucking around with the land of the living).
The sad thing about a meme is that it can't last forever. Nothing does. One day, you and I and everything we ever thought or believed in will be outdated. Steampunk says, "Not only is your old idea still useful, it's better than the cold, grey, sterile -shudder- modern world you sexy NeoVictorian, you."
In the Information Age we are forced to re-evaluate ourselves, not just our bodies and genes, but also our thoughts and feelings. If, 5000 years hence, it is discovered that everything you know is wrong, does that make it any less significant today?