Fame
The level of fame you can achieve as a public administrator depends on which kind you are. If you're a congressperson, chances are really good most people in your state have heard of you. If you're the assistant director of elder care, chances are good everyone's going to forget your name, even if you just told it to them (jerks).
For the vast majority of public administrators, especially the unelected variety, we'd hazard a guess that not being famous probably isn't an issue. After all, this job is all about public service. If you go through all the trouble to get a degree in doing so, you're aware that you probably aren't going to be making national headlines any time soon.
What's important is that your work helps the people. If anyone appreciates what you did and wants to tell all their friends, that's great, but at the end of the day you're still going to do what must be done. Go you.