If the service is not going to contain any privacy related stuff or need not be so secure why not just keep the cookie after typing in email address. What i do

If the service is not going to contain any privacy related stuff or need not be so secure why not just keep the cookie after typing in email address. What i do is i keep all worthy sites'password on the password manager and the rest of the site follow a pattern based password or a common simple password. For e.g. i typically use some this "keepass"or domain of visited web + keepass