FRONT SQUATS HELP TO MAINTAIN A STRONG UPRIGHT POSITION
Front Squats need strength in the upper middle back to support the weight during the eccentric portion of the squat (as you lower the weight down). Without this you will tip forwards and drop the weight.
Because of the bar path, the front squat forces you to bend at the ankles and knees way more than at the hips. Your hips and ass need to be underneath the bar in order to provide a stable position to move the weight and complete the reps.
Developing a strong upright position on the front squat will also help to strengthen and promote an upright position for the back squat. It’s common to see athletes bending too far forward (once back squats get too heavy) into something that resembles a good morning in order to try and compensate for the lack of strength or mobility that is forcing them into this position. The front squat can be a good way to reinforce an upright position and build the strength, confidence and mobility to improve it for the back squat as well.