When registering, some websites ask for the email on one screen and the password on a later screen. LastPass stores the password, but not the email. I can manually enter the email when I try to log back in or edit the entry in the LastPass vault to set the email as the username, but there should be a way to automate this process.
Also, when trying to log into these sites if I haven't manually set the username to the email address, LastPass won't offer to autofill the email address, even though the web page explicitly asks for an email. I have turned on address autofill in Chrome to get around this problem, but I shouldn't have to do that.