Unlike Tritium, Radium (specifically 226Ra) emits mainly alpha particles which would be useful for luminescence, but it is very toxic to living tissue. (Tritium emits far less energetic beta rays.) However, unlike Tritium, it is a solid and if the container holding it breaks for some reason, then a highly ionizing source of radiation is susceptible to ingestion. If the Tritium container breaks, the gas is quickly dissipated into the atmosphere. Even if it is inhaled, it is fairly quickly exhaled and practically never reacts with living tissue.
The same can be said of Thorium, but it emits alpha particles at a far lower rate so it is not quite as toxic as Radium. But, it is still a well known carcinogen when ingested.
In short, those elements aren't used for safety reasons.