There's different kinds of information that law enforcement can store.
Looking at extremes: keeping a record of which people have killed someone in the past seems like a very reasonable thing to do. On the other hand, keeping a record of how long each person brushes their teeth on average, seems like an invasion of privacy (and pointless when it comes to anti-terrorism).
Taking photos of an already well-photographed public landmark seems to fall in the latter category.
Looking at extremes: keeping a record of which people have killed someone in the past seems like a very reasonable thing to do. On the other hand, keeping a record of how long each person brushes their teeth on average, seems like an invasion of privacy (and pointless when it comes to anti-terrorism).
Taking photos of an already well-photographed public landmark seems to fall in the latter category.