When I used to have carry-ons, boarding early ensured that I got room in the overhead bins to place the bag. I now use under-seater bags only and pack light so I no longer care when I get to my seat.
Lastly, there is always the risk of a lost bag once you no longer have it with you. One fight years ago they forgot to load all of the car seats and gate checked bags that were left at the end of the ramp. We were stuck waiting 90 minutes for the next flight from that destination to arrive since we needed the car seat to drive our child home.