To maybe oversimplify it, cancer risk from radiation is all a stats game. The situations where you get a CT scan is either very rare (once or twice in a lifetime and often highly localized) or for a very acute issue (eg a heart attack or car accident) that is almost certainly worth the risks.

Also, ionizing radiation has a varying risks to different tissues. "Soft" tissues that have cells that divide a lot (lungs, colon, etc) are of greater risk than others. I wouldn't bat much of an eye for a CT scan on my knee, but would be more worried about a chest procedure. Again, more worried doesn't mean I wouldn't do it, as the alternative is either a much more expensive MRI, much more fuzzy echo-cardiogram, or wondering if my health is more seriously at risk.