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
I’d agree with you, for substantial weight
What I mean is, the weight of the clothes sit on your shoulders (which is a negligible amount), which i find much more comfortable than the weight on the hips (and the constriction required to keep pants from falling off).
Also, if you have a heavy tool like a cordless drill, you can hook them on overalls (to free up your hands) and the added weight won’t pull them down, unlike pants