It's a good question. I suspect there are several reasons: firstly, travel was not so common - families of the Napoleonic dead would have been unlikely to travel to see the graves. Second, I suspect that it was harder to identify bodies then, there wouldn't have been the detailed records...
I stand corrected. When I did my history GCE there was nothing about any battles, let alone anything about tactics. For example, we studied the aftermath of Waterloo (Vienna and all that) and nothing about the battle itself
This was 46 years ago, so things may have changed :)
To be fair, history at school doesn't really cover warfare. As you said, you learn about the causes of the Crimean War or the origins of the First World War but there are little or no details of the individual battles.
Beevor's books are nearly the opposite - the D Day book doesn't go into...