Why 10 Days?

I was unsubscribing from email mailing lists that I have been in the habit of deleteing anyway, and after opting out of Marriot.com, this is what they said:

Email Sign Up Confirmation

Scott@MyEmail.com is subscribed to:

You have chosen not to receive email.

Please allow ten business days to process this request.

Excuse me, but unless you are doing this by hand, which you are not, this is irresponsible.

That's all.