They certainly are offered for trips with connections. Now that they're back with simplified offers for the route, rather than flight-specific (yay, I was able to rebook a Saturday flight at a lower fare), they show many with connections. My trip is MCI-LAS, where it's preferable to go non-stop, but the DING is available on trips with connections. When they show flight-specific DINGs, many of them are on connecting flights.