Because there's Harry Potter and Just Harry. And heroes aren't allowed to bleed.
Harry Potter is the Chosen One, the Savior, the Boy-Who-Lived, the slayer of evil and darkness. He is a hero. Harry Potter is strong and undefeated. Harry Potter is the physical avatar of Hope and Light. Harry Potter is infallible.
Harry Potter doesn't spend entire days in bed, thinking of those he lost with tear tracks on his face and eyes too dry to cry anymore. That's Just Harry. Just Harry is what Harry Potter protects the most. Just Harry is his greatest weakness and his greatest strength. There are only two people in the world who can tell them apart.
Hermione breaks into uncontrollable hysterics every time she thinks about it.
Ron drops whatever he's holding and feels like kidnapping Harry, taking him away to where Harry Potter can rot and die and Just Harry doesn't have to live with a mask.
Harry Potter is strong, unbreakable, infallible. Just Harry is what keeps him human.
Potter sleeps in the cupboard under the stairs for the first ten years of his life. Harry is there every morning to make breakfast and be sure Potter hasn't killed the Dursleys in their sleep. Harry doesn't let Potter fight back, because they know they'll win. Potter kills Quirrell because Harry can't stop him. Potter kills Riddle because Harry doesn't want to stop him. Harry spares Pettigrew to prove to the both of them who is really in charge. Harry offers to share the glory with Cedric, forcing back Potter's suggestion of cursing the other boy.
Both of them fight Voldemort in the graveyard. Harry reaches for Cedric and the Cup. Potter reaches for their wand to finish the Dark Lord once and for all. Harry wins, just barely. Harry saves Dudley, and it is he who drives back the Dementors, not Potter. Potter yells at Hermione and Ron at headquarters, and they all can hear the subtext. You caused us pain. I will destroy you. Hermione cries later, for a friend with more demons than anyone should have. Ron wants to hug his best friend without worrying that he will find a knife in his back when he pulls away.
Harry sits through the trial, Harry blows up at Umbridge, but Potter sits through their detentions. Potter hates anything that causes them pain. Harry forgives. Potter never lets them forget.
Harry Potter defends them against everything, and he cannot fall because he is not human. Harry Potter is a monster worse than Voldemort, because his face is human and lies with every smile.
Just Harry keeps the world safe from himself. He cannot fall, because everything depends upon him.
Heroes aren't allowed to bleed, aren't allowed to be human. True heroes don't come home.
Just Harry and Harry Potter tell everyone they're not heroes, true or otherwise. They're still trying to figure out if that's a lie or not.
Hermione realizes her friend is two different people when he tells her how he killed Quirrell and doesn't flinch or regret.
Ron knows the night he wakes to Potter standing over him, with wand in hand and ice cold eyes. The boy whispers If you ever harm us I will make you will regret it. Ron thinks it's a dream until he tells Hermione about it and she glances around nervously and she says they're safe as long as Harry is.
Maybe it makes him fight just a little bit harder, but he is only human.
Not what I was going for when I started, but the muse insisted. I like how Just Harry can be interepreted as merely or only, and also as fair or even. I actualy write/read Harry Potter fanfics the most; it's such a versatile fandom.