Why is there no games based on World war 1?

[Reasonable]

Lostplanet22 said:
USA was not involved like in WWII. It was a war based on one front, A game like Valkyria Chronicles would be the best gameplay for a WWI game in my opinion.

While USA was not involved nearly the same way as WWII it was somewhat involved in WWI, most countries actually were if you really look at the history.  For example, Native American Indians actually fought in WWI.