And a mage wets their appetite just well! And may even be useful for the rest of the party at the same time.
(also, "run up and hit it with a sword" characters may inadventedly become a laughingstock of the party (or get bored themselves, which is even worse) - which may defeat the purpose of getting new player in the first place)
And of course it doesn't cover the whole game - they'll need to learn tactics, etc. Which is, by the way, why, say, Abyssia (or Sauromatia) may be a good nation for a start - true, starting player may not be successful with a Bloof - but he could try it while his powerful infantry fights off any opposition (and in DD newby mage can try something wacky whilr fighters hold enemy off him - which they wouldn't do for another fighter!).