"Free members can initiate and receive calls, but they can't read or respond to messages."
Free members aren't able to initiate messages. I suspect that if somebody receives one from a Free Member the message was sent prior to their paid membership expiring. Free members can receive messages but they can't read/respond to them.
"...profiles that posted alternative contact info who were running sextortion scams...."
Unlimited members who approve profiles should have caught the outside contact info and flagged the profile before it went "live". Many times the contact info is inserted cryptically and not everyone who reviews profiles catch it. If you run across a profile with outside contact info you should report it to management.
"Some might have bought a membership and then canceled it. Why they didn't delete their profile is beyond my understanding."
Usually people just let their paid membership expire. Unlimited memberships don't expire, if unlimited members "cancel", they most likely tell management to delete the profile. I'd wager that some unlimited members just lost interest, didn't return and either forgot the log in info or just don't care.
Or they died and didn't have the courtesy to tell management that they're dead.