An automobile recall is a good analogy here.

Most people driving cars with an active recall are unaffected by the problem the recall is supposed to address. They can drive on blissfully unaware that something could go wrong. They might even enthusiastically recommend that others purchase the car they drive.

For a few people, they'll experience a failure, possibly a dangerous one.

And this is the root of the problem. The fundamental concept of using a language prone to UB exposes all programs to a small risk. In isolation, the risk is small. In aggregate, the problem is real.