Generally bags can connect faster than people. I only check bags IF I have a tight connection and don't want to lug them around with me.

Plus, the airline generally has a higher liability for misconnected bags than for misconnected people, so they often pay more attention to bags misconnecting. If you misconnect, the cost to the airline is a seat on the next flight ($0 so long as there is an empty seat). If a bag misconnects without you, their obligation is to get it to your final destination (home/hotel), which costs them real cash in handling and delivery costs.