Want to start on level 1? Okay, but make it level ONE: 3d6 in order, no special abilities, and keep a blank character sheet just in case. No half measures. You either die a victim or survive long enough to become an hero. And then die.
Want to start with a competent character? Start at level 3.
Well, anyway, it works for me. Here is why.
1. 1st level are victims. They are likely to die if they fight a couple of house cats or fall from a tree.
2. Everybody wants to be a hero. But what if we don't? If first level characters are heroes, we cannot play weaker characters because they barely exist.
3. Normal humans (Moldvay) have 1d4 HP. A blacksmith may have 4 HP and a young child, 1. They still fight like 1st level Fighters, and half a dozen children may kill the fighter in a couple rounds if they attack first.
4. HP inflation. Every gets one HD per level, right? But almost EVERY VERSION of D&D has some different rule why this shouldn't apply to level 1. Maximum HP at level 1, double hit dice at the beginning, starting HP equal to Constitution score, etc. Well, why not start on level 3 instead!
5. 1st level characters become too complex when you want them to be heroes. Take 5e, for example: you start with a background, two or three features from race or class, maybe a feat if you're a human, etc. Where do we go if we want to start simpler?
6. 5e wants you to get to level 3 soon, that is why so little XP is needed in the beginning. Well, if that is the case, why not let 1st level cahrachters be simpler so you make choices later on?
7. In fact, 5e DOES leave some choices to level 3. You cannot choose to be an assassin or thief until level 3, for example. So if you want to start as a thief, start on level 3.
8. Dark Sun did it. Or something like that, I think... And Dark Sun is awesome.
9. Gygax did it. 'Nuff said.
10. You cannot have meaningful single-digit characters and fractional skill unless you start on level 3.
11. If everyone starts on level 1 the Deprived Class loses its meaning.
12. I was reading the 5e Volo's guide the other day... An apprentice wizard has 2d8 HP. And he is a first level spell-caster. So your wizard is not even an apprentice on level 1.
13. Have you written a background? If you took the time to write one, maybe you should have a few extra HP so you don't die in the first round of combat.
14. Start on level 3 and now you level 10 character is only three or four times tougher, instead of ten times. Everything makes more sense, not only falling damage and the amount of arrows you can take before dying.
15. Most "modern" methods of rolling abilities (4d6 drop lowest, etc.) create heroic, strong, competent cahrachters... with about half a dozen HP. How come?
16. Granularity. If most heroes are level three, you can have a level 2 squire, a level 1 peasant, and a level 0 child, for example. A veteran would be level 4 instead of level 1. You could face a few - A FEW - goblins or kobolds at the beginning of the campaign and survive to tell the tale.
17. Arneson suggests HP are meant preserve characters because people get attached to them. If I must spend more than 10 minutes creating a character, he should have a few extra HP and probably some skill to go with it.
18. Also, first level characters were meant for Chainmail. Once we zoom in on the PCs instead of looking at the battlefield, more HP is obviously useful.
19. A first level wizard in Basic may have the same amount of HP as a young child if the GM isn't using optional rules. First level thieves are really bad at skills. First level clerics don't even have cleric spells.
20. In fact, the Basic fighter doesn't even get an attack bonus until level 4. Maybe we should start on level 4 instead? Nah, that is obviously too much!
Yes, some of them emphasize or contradict the others. This is "roll 1d20" table, not "read my arguments carefully and make an informed decision"!
(note: I had to republish this to make LinkWithin work as intended; hope it does the trick).