The weight of the material is supported by your shoulders, and not your hips, which is far more comfortable in general
In addition to having more room for pockets, overalls can carry heavier things without falling down, nor need for a belt
Since the weight of the material is carried at the shoulders, bending down at the waist is easier and less restricted. The waistband no longer needs to be tight, since it no longer serves a functional purpose
This is correct, and for anyone looking for proof all you have to do is inspect a hiking backpack and note why they have sturdy waist straps – to transfer the load from your shoulders to your hips. Your legs and hips are designed for supporting the rest of your body weight all day long. Your shoulders are not. If you put a heavy load on them full time (in this case, perhaps lots of stuff in your overalls pockets) you’ll quickly find this out first hand. And furthermore, a constant load on your shoulders gets borne by the entirety of your spine.