Historical Gaming without Magic or Alternative History
If I see a game based on the Old West it's a pretty safe bet that the Confederacy is still alive and kicking. Similarly, there have been games set in the Roman Empire that have vampires and or beasties of the Cthulhu Mythos.
What I'm writing about is the tendency of historic RPGs to take place in an alternate past, usually with some fantastic elements. It's not a universal tendency - for example, TSR had both Boot Hill and Gangbusters, covering the Old West and the Prohibition-era. But I'm pretty sure that's a minority. And to be fair, there's not a lot of games set in the modern age that don't bend reality pretty hard - typically with a heavy dose of the supernatural or of superpowers.
I get the inclination to play with history and add the magic - setting a game in a historical era can feel a bit overwhelming and changing the past gives a lot more leeway for historical inaccuracy - "what do you mean you're upset that Perceval is listed as becoming Prime Minister in September instead of October of 1809 - the presence of dragons changes everything!"
That said, there's a few eras I'd love to see embraced as they were for gaming opportunities. The first of these would be the French Revolutionary and Napoleonic Wars. Patrick O'Brian's Aubrey/Maturin series shows how exciting the era can be - there's room for naval battles, boarding actions, land combat, duels, courtship, politics, etc.
The Prohibition-era also seems to scream for a bit of love. It's likely players in such a game would be running the bad guys, but the gaming opportunities seem fantastic - build your gang from nothing to a criminal empire. Take on rival gangs. Make alliances. Avoid or bribe the law. Try to hold on to some moral code. I was a big fan of HBO's Boardwalk Empire which gave us a fictionalized account of Prohibition-era Atlantic City.