Why Limit Steampunk?

This quibble has been niggling at my mind for a while: why is all steampunk Victorian?
It's a fascinating era, to be sure. And I can see why the age of the Industrial Revolution would lend itself nicely to a world of wild inventions. But there was more to the past that the Victorian; more ages that might work equally well.
 Why not try for a Renaissance Steampunk? Say Leonardo da Vinci put his inventions into action, most of them actually worked, and this kicks off a wild inventing spree in Italy. Alchemists figure out chemical reactions that actually work. Some decry this as black magic; others find it interesting and get into it themselves. Inventors scramble to find sponsors--the Borgia popes and Frederick Barbarossa II. Travel is revolutionized, and people question whether their flying machines should be used for conquest or to help spread the Word of God.
Or try an Ancient Greek steampunk. Believe it or not, steam power was actually invented in Ancient Greece, by an inventor named Heron. His little steam engine never got above being a toy...but imagine triremes and chariots powered by steam engines. Imagine the war engines of Archimedes--and what he could have come up with if he'd survived that siege! Imagine the ancient world if the inventors got a little more credit--and took their work further.
Imagine steampunk technology in colonial or Exploration times. Why not send Christopher Columbus on his trip across the Atlantic in a silken balloon?
And on the supernatural side of things, why limit Steampunk to werewolves and vampires? Not all stories do this, admittedly; one of my favorites, Tales of the Brass Griffin, (unfortunately discontinued) admirably mixes the more common fantasy races into the setting of the world. But take it further! Perhaps the realm of Faerie objects to the spreading of technology and iron everywhere? Perhaps Faerie takes advantage of a world growing blind to their presence? Would the Fae realm be fighting to survive...or enjoying the changes?
Maybe that dashing young man romancing solitary girls by night isn't a vampire at all, but the dangerous Ganconer. Perhaps a riverside town is haunted by strange songs that rise from the depths of the water each night, as nixies and river-nymphs congregate. Perhaps whispered tales are told of a stray 'cart-horse' roaming the area: in reality, a Kelpie seeking prey. A wood is carefully avoided by those old folk who remember the stories of it; but the youngsters and newcomers don't believe the tales, and enter freely--only to find that the stories are, in fact, true. A wealthy factory owner tries to buy out a town and farmland to put more mills on, and kicks off a war with the Fae beings who live in the area...but are they fighting for the farmers, or will the farmers and townsfolk just get caught in the crossfire?

Steampunk is such a wonderful, versatile genre. Don't limit it to what's popular now!