That "Mercury retrograde" (if they're even aware of it) is superstition, and has no actual effect on what they do? That would be my guess.

Honestly, people talk about that as if it were some incredibly rare planetary conjunction or something. It's a perfectly normal consequence of celestial mechanics. Of course, the people who originally came up with the idea had no notion of celestial mechanics at all, and thought the sun revolved around the earth.