Czech cemeteries - why there are no old gravestones?

There is one request which appears repeatedly in the guide requests I get - can we visit a local cemetery and look for the gravestones of my family? 

Sure we can. We can walk around the parish cemetery to which the village/town your ancestors lived in belonged. But if your ancestors immigrated to the U.S. hundred and more years ago, we most probably won't find them. Why?

German-speaking inhabitants of the Czech lands

I found an interesting map of the percentage of native German speaking inhabitants in the court districts of the Czech lands before the WWII. It shows the density of the German speaking population in the border area - Czechoslovakia was forced to give up these parts of the country to Germany in the Munich agreement of 1938.