The buyer under the current contract may have made a contingent offer with a kickout option, providing the seller a short while to receive a back-up offer. Another scenario where this may be happen is in a development consisting of essentially identical units, as in duplexes or town-homes, and the existing unsold units may not be finished enough to show. The only other reason would be if the home went under contract and the advertising for the open house had already been submitted and the Realtor feels obligated to proceed with it regardless. - Mon Mar 5, 2012