As I've traveled more and gotten older, I'm actually regularly downsizing my bag size. With packing cubes, space optimization, and just overall prioritizing the essentials, I usually go backpack only for most 1-2 day trips and international carry-on size for 2-5 day trips. I still have a domestic carry-on size bag that I use for 5-7 day trips.
It's not for everyone, but packing light is liberating to me--it just took 15 years for me to figure that out and how to do it.