What remains is: all those quirky little one-off processes that aren't very amenable to "robot arm" automation, aren't worth the process design effort to make them amenable to it, and are currently solved by human labor.
Thus, you design new solutions to target that open niche.
Humans aren't perfect at anything, but they are passable at everything. Universal worker robots attempt to replicate that.
"A drop-in replacement for simple human labor" is a very lucrative thing, assuming one could pull it off. And that favors humanoid hulls.
Not that it's the form that's the bottleneck for that, not really. The problem of universal robots is fundamentally an AI problem. Today, we could build a humanoid body that could mechanically perform over 90% of all industrial tasks performed by humans, but not the AI that would actually make it do it.