The reason typically is that most people have difficulty interpreting protective ORs, those under a value of '1'. Also, if your scenario above is what you plan to do, you may have some type of immortality bias or survival bias. The rate of smoking in older persons may be higher, but the smoking based sequelae may have manifested itself and they die (lost to follow-up) or are less likely to provide info since they are institutionalized. There are impacts from smoking.