There is no obligation, but it's obvious it's a condensed and pertinent information about human being to know about their lifescope (or year of birth when the person is still alive), and by removing it systematically like you are doing it cannot be helpful, in any circonstance, this can only cause trouble. I don't understand why you are talking about pollution and facts, this is obviously a fact and no pollution. I have already lost a lot of time trying to find a good homonym because dates were missing, it depends on the data one is handling, having the dates directly can be very helpful in some cases. Also, you cannot reason from a static current situation, the database is dynamic and new items are added constantly, so it's also better not to have to lose time to desambiguate constantly the item's descriptions.