We used to have an informal standard that a person known to be still alive should have just the birth year in the page name, as an indication that the person has not yet acquired a death year. Disadvantage is that the person may have died by the next time anyone looks at the article, so there is no certainty in the omission of the hyphen.
Some contributors have nevertheless added such hyphens, possibly having forgotten or not read the standard. So the distinction has lost its force.
Everyone will need a hyphen eventually, so there is no ultimate saving in omitting it now. Making the hyphen standard for all people, alive or dead, will reduce the risk of duplication and the time-wasting that has sometimes seen some well-meaning contributor adding or deleting a hyphen, depending on his or her view of the standard. Another small advantage is that the inclusion of the hyphen will make it clearer that the one date is the birth year, not the death year or a "floruit" year.
Let's include the hyphen routinely after the birth year (but not bothering to add them to existing pages unless another change is needed).