nyc_naturalizer
Registered Users (C)
This makes some sense, but creates terrible inefficiency. The end result is that more people are waiting longer between LPR approval and N-400 ajudication, thus creating more "background" to "check," more likelihood of false hits on names, etc. There should be an assumption that an LPR may want to naturalize at some point, and the system of security checks for both applications streamlined.
I just told you why a background check is done for N-400 applicants. They want one more chance to catch any thing the LPR has done in the past, but with more emphasis on the time between LPR approval and N-400 adjudication. This way they often catch LPRs who have domestic warrants too.