In the last twenty-five years I've been in dozens of games that started at 1st. level. It's gotten kind of boring to make a character with a "promise of greatness", and watch the game peter out after a level or three, because nobody had the endurance to play week after week, year after year to get characters up to a name level.
I think it points up the dichotomy between two basic styles of making characters: "define in play", and "define then play": the former is basically classic gaming: you roll up a random character, one with no history and personality, and gradually build up a character in play. the alternative, which really stated to come into its own when Champions came around, is to develop a character and history, and then arrange the stats to match.
My friends and I prefer the latter method, because really, life is too short, we're all too old, and we're all really busy people. If the game is likely to only last a dozen or so sessions anyway, why not make the characters where we want them to be?
There are twenty levels of character development, and in a 1-20 game, it's highly unlikely our groups will be around to even taste the higher levels. So, if my SO wants to play an Inigo Montoya or Lina Inverse, she's not going to be very happy if I make her play a Neville Longbottom for the first six months of the game.