Surprisingly New Vegas Radio has more songs than Galaxy News, GNR had 20 and NVR has 25. Well, actually 24 since the developer who setup the play list accidently assigned "Big Iron" to "Stars of the Midnight Range" so Big Iron has two spots on NVR while Stars won't play at all. I think the reason that it seems like less is because there's often only one song in between Mr. Vegas' news broadcasts, and the game has this annoying tendency of playing the same few songs over and over again... a problem that was present in Fallout 3 as well.
Where are you pulling these numbers from?
* "Ain't That a Kick in the Head?"
* "Big Iron"
* "Blue Moon"
* "Cobwebs and Rainbows"
* "Heartaches by the Number"
* "It's a Sin to Tell a Lie"
* "Jingle, Jangle, Jingle"
* "Johnny Guitar"
* "Let's Ride Into the Sunset Together"
* "Love Me as Though There Were No Tomorrow"
* "Mad About the Boy"
* "Sit and Dream"
* "Something's Gotta Give"
* "Why Don't You Do Right? (Get Me Some Money Too!)"
Those are the only songs that play in game on NVR. 14 songs. The song list needs expanding badly whether or not there is a bug in the game prevent some songs from being played. All these people claiming it has 20 songs or whatever are misinformed or not reading their source correctly. There are some songs in the game that are not intended for use on the radio and are used in certain locations/events. There are
FOURTEEN songs for NVR and they are not weighted evenly. You will hear certain songs a lot more than others and its not uncommon for a song to show up twice in a row or with one song apart.