Because Roosevelt raised the need to renew the court, that is to say to enter young judges before the refusal of many judges of advanced age who did not contemplate to retire. This initiative was not accepted and was considered unconstitutional, for which it received little support and it was there that the president suffered his first defeat in his intention to appoint more judges to the Supreme Court of Justice.
According to his critics, President Roosevelt proposed increasing the number of justices on the Supreme Court because he knew some of them would resign--meaning he could "pack the court".
