I found this flowchart describing how to get a PE license in one state (CA) interesting. Such charts differ by state. Note the buttons can be selected to bring up other charts or pages.
https://www.bpelsg.ca.gov/applicants/flowchart_for_pe.pdf
For what it’s worth, whenever I search for the percentage of engineers who have PE licenses I get ~20%. I think the source cited by others was the National Society of Professional Engineers, but I haven’t found their actual study so don’t know how they came up with that figure. But it seems safe to say a PE license will be very important in some cases, but not essential in others.