Yeah but then you'd go through life having biopsies all the time. If all people did a full body MRI almost everyone would have weird lumps that doctors would have to biopsy to be really sure, and then what do you do? Do you biopsy yourself every time some weird tissue appears? Most of those will be nothing and you'll be going through the complications of surgeries and anesthesia all the time just to always make sure.

That's true in the case someone actually does have cancer, but what about paying for all the negative tests?

Nope, the cost is 5-10k maybe more, and there is alot of nuance and follow ups to those detections