Neither serve any purpose.
I disagree. At least partly.
When my friends and me started playing, we enjoyed fighting the novice games with one of the recommended (unlocked) ship-presets. It helped us getting a feeling for the mechanics without getting ripped apart by experienced players. Although we would have been happy to play on more than only two maps ... I have to mention that we started during a sale though.
Besides that I now still like the feature because it improves the quality of higher ranked matches (at least a bit) by filtering out all too inexperienced players. That's good for both, novices and advanced players. Teaming up and teaching other new players is more fun when they at least have played a couple of games and got familiar with the basic mechanics.
Relating to the vet games I have to say, that I rarely had the opportunity to play one unfortunately. But the few ones I played were quite fun (and also challenging). That might have been because of the huge number of friends playing there though.
In summary that means, the novice matches are a very useful yet slightly improvable (e.g. ships & presets, maps, levelcap) feature which I advocate 100%. I don't have an idea for a different system which gets around the limited player count problem. Regarding the vet games ... I'd really like to play some more before judging them.