Actually a 4e fighter can start with nearly 30 HP. But people who freak when they look at the number, do so because their expectations are grounded in prior edition math.
HP in a vacuum are meaningless. If I have 30 HP, but a kobold can do 50 HP of damage on a hit, then I'm playing a game more lethal than 1e AD&D. What HP do is give you a number that work in tandem with hit percentage and avg. damage output that you can use to set the lethality and playability of your game.
People are getting way too caught up in fiddly verisimilitude and simulationist notions of how many HP a human should have or be able to do, but none of that matters.
You have to look at the big picture first. How durable should the party be as a whole? How many encounters should they be able to overcome before resting? Then start breaking that down into smaller elements. How durable should the Fighter be, the Rogue, the Wizard and so on. How much damage should a monster output? How much can it take? Some of these decisions are already partially set simply by virtue of using d4, d6, d8, d10, and d12 dice for weapons.
Then what hit percentage feels fun, without being automatic, and without leading to frustration after successive misses. Also you have to consider that missing or hitting too often also has an effect on durability when considered with HP totals, damage output and combat length.
Then once you have baselines, you can go back and forth from micro (individual PC damage and HP) to macro (party durability and recoverability as a whole), fine tuning and tweaking as needed for balance, fun, and yes a bit of verisimilitude.
This is also why I also firmly believe that randomness has a place in adding variability, unpredictably, and tension to say combat, or any scenario where success is in doubt, but has no place in character creation. Rolling too high, or too low for stats, or HP can completely screw with the expectations of one's game. Over my 25 years of playing D&D, I have seen many DM's and/or players get frustrated because PCs are too effective, or not effective enough, all as a direct result of randomness in character creation throwing off the underlying balance expectations of the game.