Why Airlines Default to Charging for Check Bags but Allow Some Level of Free Cabin Bags

Susan, it's been great having you with us. Why do airlines default to charging for check bags but allow some level of free cabin bags? Shouldn't it be the other way around as a default? Every check bags and fees for anything in the overhead bin, unless you are a frequent fire or co-branded credit holder, etc. Today's incentives seem perverse causing longer passenger loading and unloading times at gates.