At high-volume airports gates aren't assigned until the plane has arrived from it's inbound flight which is often <1hr from departure time. Checkin generally o

At high-volume airports gates aren't assigned until the plane has arrived from it's inbound flight which is often <1hr from departure time. Checkin generally opens 24 hours prior to departure (some airlines now allow >7 days prior) - hence for the vast majority of passengers the gate is unavailable as ticket issuance time. Most airports and airlines let you get gate information fro their websites/apps as well though..