Sadly the worst thing to happen to scanning was the death of "Police Call".
IT had all the licensed channels in one book. Maybe Licensed and rarely used, but it was there. Some channels just never get used except for the BIG ONE, others all the time. It's a matter of searching and reporting.
The RRDB and the SNE Wiki rely on Submitted and Verified use frequencies. If its not submitted by someone, it's not there.
There are lists [many on yahoo] that post the recent FCC transactions which is a good place to watch as the NEW licenses are issued, as well as the old ones Modified or Renewed, plug them in, see what you hear and most of all SUBMIT them back to the Database.
Remember, altho its December the RR Fairy needs your help in keeping the DB updated, and to steal from Smokey Bear - "Only You Can Keep the Database Accurate"
Even scanner enthusiasts should know some frequencies just aren't published. Think what you want about open access, etc. It's about Everyone Going Home. These would be Special Ops, Surveillance frequencies, etc. Not the little know security or other channel used from time-to-time. They're game.
Then as ecps92 said, people want to get all the info from somewhere w/out looking or putting any effort in.
Then finally, you can submit info to RR for Malls, and lesser known frequencies here all ya want. if you're lucky they might be published. I had a bunch I submitted a couple months ago or more and they just made it in. Those replaced previous submissions that were never published.