The password field is automatically required because it is necessary for login.
You can adjust the validation on the pages manually after application if it doesn't fit your needs.
To make it not required on the update page, just remove the required attribute from the <input> tag itself and update the Server Validations server behavior to remove the password validation that is there.
Then you will want make sure it uses the existing password if the field is left blank. If you attach a copy of your page I can give you a code sample of how to do it.