Li Shenron
Legend
I don't think that so many groups start at third level is a feature of 3.5, I think it's a bug. I think that people start at 3rd level not because of a desire for a particular power level, but because of a desire to play the game during the segment where the math, customizability, combat engine, magic item system, spell system and a few other subsystems come together to produce the edition's best experiences. I think that if the first two levels weren't comparatively boring, more people would start there. Campaign time is too precious for a lot of people to blow a bunch of it outside of the sweet spot. I'd hope that Next absolutely does not have the property that one level range shines much brighter than the rest of the level range in terms of how well the system works. I'd like for it to all be fantastic.
Yes these are precisely the reasons!
But it's not the bug. The bug is that even 1st level is a bit too much for old-school grim'n'gritty, and one of the most common reason for several old-schooler to never switch to 3e, because their felt their favourite gamestyle was unsupported.
And if 3e had started at 1st level with characters equivalent to 3rd level, that would have been two bugs, because it would have made it very hard for beginners and casual players, less likely to get hooked to the game.
As [MENTION=6690511]GX.Sigma[/MENTION] said, beginners and old-schooler are the target of the apprentice level idea. You're neither of them, and neither am I (except that I might want to play more old-school sometimes, and I might need to run the game for beginners as well), but why not wanting them in the target audience when we can still play our way starting at 5th instead of 3rd as in ed?