Asimov addressed this in one of his robot novels. Need your lawn mowed? If you already have a mower, your humanoid robot can use it. Dishes? It can stand at the sink and do them. Drive you somewhere? It fits in your car and can use the controls designed for humans. And if the robot breaks down, a human can take over.

Basically, instead of one robot per task, have one robot to do all the tasks using tools designed for humans.

But you’re right, if the robot is only going to do one thing like work on an assembly line for cars, a custom single-task design makes sense.