Why do some people who do not have shy bladder syndrome repeatedly ignore the urge to urinate when they could find a restroom fairly easily and take care of it?

Sometimes, those people do not want to be bothered by it. It is unhealthy to hold it. They are putting themselves at risk for infections.

Agreed! Plus, if they severely stretch out their bladders, the detrusor muscle can become so weakened they'll need to urinate by catheterization at some point, for the rest of their lives.