Why would anybody have in a graveyard? Isn't that a bit...?

disrespectful? Is this supposed to be normal? Me and my friends were exploring and playing around near the woods and we found an old abandoned graveyard. We thought nobody was there so we were just reading inscriptions and looking around. Then we saw two people having or close anyways(I haven't really seen anybody have I'm only 10.) We just walked away slowly. Why would anybody do that? It's do disgusting.