Manipulation

Why picking things up is hard.

Moravec paradox

Chess fell to computers decades before reliable grasping of unfamiliar objects. Perception and physical dexterity are far harder to automate than reasoning, because evolution spent far longer on them.

Contact forces are hard to model and vary with surface and shape.
Soft and compliant grippers succeed by tolerating error rather than eliminating it.

Structured environments

Factory arms succeed because the parts arrive in known positions. Remove that structure and the same arm fails, which is why warehouse automation invests so heavily in fixtures.