Fame
The most famous park ranger ever is probably Ranger Smith of Jellystone. What? You don’t remember him? You never watched Yogi Bear? C'mon, it's on Boomerang. How about the 2010 remake featuring the vocal talents of Justin Timberlake and Dan Aykroyd? Guess you missed that one, too (along with everybody else).
Anyway, when the most well-known member of your profession is an animated character who most kids these days have never heard of, you can be pretty sure it won't make you famous. The second most famous guy who was ever a park ranger is probably Gerald Ford, but we're thinking that whole being the president thing is what got his name in the history books.
We have a feeling that certain park rangers must be standouts in their field. We bet there are legends out there who are whispered about in dark cabins across the U.S. But no amount of googling has revealed their identities.
The point is, you don't become a park ranger for fame; you do it for love of the job.