If it really was even actually a couple...
A couple requesting to see a home would most likely make someone feel much more at ease.
If they didn't meet at another place (out in front of the agency or a known local business that someone out of town would find easily) and so thus she didn't have whoever she was showing the home to following her, but instead met at the residence directly, if someone then showed up alone, it'd almost be too late.
An agent could be caught off guard expecting a couple and then end up there alone with just a guy (although I guess it could also be a jealous female)