Robotic surgery for treating cancer?
Actually we aren't that good at localizing cancer cells.
There need to be around 100,000 cancer cells at a single location for the cancer to be visible on fMRI.

If you want to treat a cancer via chemotherapy it's good to be able to see the cancer. It allows you to see whether the drug you are giving works.

When dealing with a metastasized cancer where you don't think you know every location in which cancer is hiding it therefore often makes sense to avoid to take out everything you can see via surgery.