Not true.
Some cemeteries welcome walkers and cyclists who just want to enjoy the place. You have to be respectful, don't buzz by anyone, remember that the place is for people to come and mourn their dead (or have their dog pee on them, depending on their situation) and act accordingly.
I think some cemeteries have problems with vandalism and other crimes, and having people respectfully using the space helps discourage that kind of thing. Too many witnesses.
