Personally, I think there is a lot of value in the exercize of studying for the PE exam. The studying itself, not just passing the exam. For many of us, the exam comes later in a career, when re-learning this stuff (or learning for the first time) can make for a re-invigoration of your career. Maybe The Civil transportation exam is narrow enough that, if you work in that field, you aren't learning anything new by studying for it. For the enviro field, studying forced me to learn several subjects that I never had a chance to work on in my professional career. After the exam, I was able to volunteer for many additional tasks in these related subjects that I would have avoided before (air pollution modeling, chemistry, hydrogeology, etc.).
I know that passing the PE is a goal in itself, and for some people who are completely satisfied with their jobs, they may never need any additional skills. These people may be able to strategize a way to pass the exam, more so than learn the material. Personally, I'd rather be working with (and hiring) the types of people who want to learn new material, and not just do the bare minimum to get by.
Still, more power to those who were able to pass without studying, or with very little studying. Everyone is different.