Mr. Chair, the answer goes to the fundamental requisites of judicial independence. One of the three requirements for judicial independence elaborated by the Supreme Court of Canada in a number of cases, including Généreux, is security of tenure. In order not to violate security of tenure, you have to have a retirement age fixed by law—in other words, an age at which the person ceases to hold office, in this case 60—but it's also possible that the person may decide himself or herself that they no longer wish to do that. In this case, it's because it's their voluntary choice to cease office. That doesn't infringe their security of tenure.
The short answer to the question is that it's necessary to contemplate the situation where the person himself or herself wishes to cease holding office in order to respect the requisites of security of tenure, which is one of the fundamental requirements of judicial independence.