Ultimately its a balancing act between what we can know and what we can do about it. If you can’t treat a cancer (or your treatment is not effective, cf the radical mastectomy) then knowing who has it doesn’t help. As technology progresses and more cancers become readily treatable, it will make more sense to do early screening, and potentially full body MRIs.

But right now it is likely to cause a huge waste of time, resources, and yes, human lives to know about every little lump in your body.