Actually "seeing nothing" is quite rare. Most legally blind people have some vision left. Many see rough shapes, and bigger patches of light and dark. Even pretty far down that scale when you would say they see "nothing", the very most people still have a sensation of "light" and "dark".

Not sure if this is a joke... but just in case: In many places it's common to decorate graves with all sorts of plants.

I think people who visit their gone relatives in the cemetery are more likely to care about others, be respectful, and wanting their loved ones rest in a nice environment. That's why a deposit isn't necessary (in most places).