Only a couple of reasons for your wife to exit that i can think of (I'm sure someone will come up with another). One is if she is arriving from an international flight which is not pre-cleared for immigration/customs. Flights from Canada and Dublin are usually cleared for customs/immigration. Maybe a couple others.

The only other exception I can think of is if she is arriving on one airline and your trip is on a different airline. Depending on the airport, she may need to exit the secured area to go to a different terminal/concourse, even for wholly domestic itineraries. LaGuardia comes to mind. If it's an airport where all domestic terminals are connected airside, no issues.

Can you share the airport and airline(s), and whether your wife's first flight is domestic or international?