The point of starting low workout is no different than car engine, I'll elaborate.
You build muscle as you go, as you progress.
If you're going uphill and begin to "plateau" in a vehicle, it wouldn't get you anywhere increasing the gears, you would DECREASE the gears back to a lower gear and build up speed to start over.
When you go to plateau in weightlifting, the same principles can apply. You would simply go back to the missing link, by decreasing the weight you re-build the muscle on an attempt to apply more weight and break the plateau.
Jumping directly into a 185 lb squat which would be difficult to me even at my prime when I have squatted in six months wouldn't make sense, starting at a low weight, practicing form and allowing my body to get used to the movement while increasing weight as I go on the other hand, would.
The weight will be increased as I go, therefore soon enough I'll be at the plateau for squats (I go until my hamstrings and calves touch), I'll most likely be able to beat it seeing I'm starting over and producing new muscle as I go in relation to just simply going back into heavy squatting and sticking at a plateau at 185 lbs for reps.