Why didn't Sauron create more Nazgul?

In this video, we look at the possible reasons why Sauron never tried or succeeded in creating more Nazgul. Thanks to my patrons - Hallimar Rathlorn, Habimana, Ben Jeffrey, Harry Evett, Mojtaba Ro, Moe L, Paul Leone, Barbossa, mncb1o, Carrot Ifson, Andrew Welch and Catherine Berry. Patreon -   / darthgandalf