Being an Electronics Engineer, I live in both sides of this equation. Take this example:
Builders do the dumbest things you can imagine, which further compounds issues. For example, my 3000 sq ft house has a second floor laundry near the front of the house, and the breaker panel is in the basement on the opposite side near the back. In their infinite wisdom, they ran 14/3 Romex for the circuit that powers the clothes washing machine, which is some 130 feet long. The punch line is this: they used the other leg on that 14/3 for lighting in the first floor. Every time the clothes washer was running and switched cycles, the lights would flare. No wonder they would burn out so often, with all that excess back-current! I fixed the problem by running a new 14/2 circuit just for the lighting, and one day, when I feel more motivated, I’ll run a new 12/2 for the 15 amp circuit feeding that clothes washer.
Builders do the dumbest things you can imagine, which further compounds issues. For example, my 3000 sq ft house has a second floor laundry near the front of the house, and the breaker panel is in the basement on the opposite side near the back. In their infinite wisdom, they ran 14/3 Romex for the circuit that powers the clothes washing machine, which is some 130 feet long. The punch line is this: they used the other leg on that 14/3 for lighting in the first floor. Every time the clothes washer was running and switched cycles, the lights would flare. No wonder they would burn out so often, with all that excess back-current! I fixed the problem by running a new 14/2 circuit just for the lighting, and one day, when I feel more motivated, I’ll run a new 12/2 for the 15 amp circuit feeding that clothes washer.