It's easier to build a specialized robot for one task than to create a general purpose robot to handle that task. However, as the technology matures, I think it becomes much more practical to create a general purpose robot that's capable of performing millions of tasks than to create millions of different specialized robots. Not only is that far less to design, source parts for, build and maintain, but it also makes it much easier to repurpose them as needs change. The same basic design can potentially be used for factory work, household chores, new construction, search and rescue operations, food service, vehicle maintenance, mining, caring for kids/elderly/pets, building and maintaining other robots, etc. We're not there yet, but that's where this kind of technology could potentially take us.

The advantage of a mostly humanoid robot is that it's versatile and can use existing solutions built for people. Yes, you could replace the legs with wheels or treads, and you'd probably be just fine for most functions with a Johnny 5 type design, but there will still be exceptions. Being able to climb up or down a ladder for example means that you don't have to engineer a solution to deal with getting onto a roof or down into a tunnel system. We've already spent thousands of years solving those problems for humans.