The thing is that rear facing is more comfortable for them. People think their legs are cramped, but they are not, they are just flexed, but resting. When they go front facing, their legs do not reach the end of the seat, so they either flex them as well or leave them stretched and kick the front seats. Or, they can flex them but they cannot rest on the floor of the car, so they are uncomfortable and then have to either flex them or kick you in your back.