Because she could have fought a bit harder...

'I've come to bring Harry to his aunt and uncle. They're the only family he has left now.'
McGonagall gaped at the Headmaster. This couldn't be right. 'You don't mean — you can't mean the people who live here? Dumbledore — you can't. I've been watching them all day. You couldn't find two people who are less like us. And they've got this son — I saw him kicking his mother all the way up the street, screaming for sweets. Harry Potter come and live here!'
'It's the best place for him,' said Dumbledore firmly. McGonagall scowled, not believing him. 'His aunt and uncle will be able to explain everything to him when he's older. I've written them a letter.'
'A letter?' repeated Professor McGonagall faintly, sitting back down on the wall. This was madness, what happened to the Potter's Will. 'Really, Dumbledore, you think you can explain all this in a letter? These people will never understand him! He'll be famous- a legend- I wouldn't be surprised if today was known as Harry potter day in the future- there will be books written about Harry- every child in our world will know his name!'
'Exactly,' said Dumbledore, looking very seriously over the top of his half-moon glasses. "It would be enough to turn any boys head. Famous before he can walk and talk! Famous for something he won't even remember! Can't you see how much better off he'll be, growing up away from all that until he's ready to take it?'
'Being away from it doesn't mean living with them!'
He looked at her sadly, almost like he was pitying her. 'Who should he stay with then?'
She almost exploded. She could think of a few names instantly and he was pretending he was unable to come up with one in several hours. 'The Diggorys. The Longbottoms. The Weasleys. Even Remus Lupin would be a better choice.'
Dumbledore frowned again. 'Harry needs all the protection he can get-'
'So why put him with a muggle family?' She had read up on blood wards and knew they were no more powerful than normal wards. 'A wizard family will understand what's attacking him and why. Those muggles won't be able to understand, Petunia hated her sister! The boy won't even be loved. It would be far better raising him somewhere where he's understood. He will still be protected. Please Albus.'
He sighed, nodding slightly. She had convinced him.

Harry James Potter-Diggory launched through the barrier with his brother, grinning from ear to ear. Although he had crossed the barrier three times before, to wave Cedric off, this was the first time he was actually going to Hogwarts.
A camera flashed in his face and he took a step back. 'Time for an interview Mr. Potter.'
Harry glared. That wasn't his name. Before he could say anything that might get him into trouble, Cedric pushed him forward, apologising to the reporter. 'Sorry, Miss Skeeter, Harry has to get onto the train.'
Skeeter nodded, scowling. Harry smirked as she walked off and turned to face his friends. Neville Longbottom and Seamus Finnegan had been his friends since they were babies, their parents having been friends at Hogwarts. Neville was complaining about losing his toad and Seamus was laughing at his father's confused expression. Mr. Finnegan had never seen anything magical, not even going with his wife and son to Diagon Alley.
Cedric helped the eleven-year-olds load their trucks before heading off to join his own friends. The three boys searched along the train until they found an empty compartment. Neville pulled out some Exploding Snap cards and the three of them settled down for a game when the door slid open.
'D'you mind if I sit here, everywhere else is full?'
Harry glanced at Seamus, who pulled a face. They had dealt with guy too many times. Since they were little, he had wanted to know Harry, grab a piece of his fame. Although Harry didn't like to think people we're only his friends because he was famous, with this boy it was obvious.
'Sorry, we're waiting for some friends to join us.' Neville said, knowing his friends wouldn't answer. 'I think there was an almost empty carriage down the corridor.'
He pointed which way and the boy's ears turned pink. Obviously, he had just come from that way and was trying to get into their compartment. As he left, Harry turned to the others, rolling his eyes.
'D'you think he'll ever leave us alone?'
Seamus laughed and Neville chuckled. He knew it was mean but Harry was sick to death of that boy. Ever since he could remember, Ron Weasley had annoyed him and Harry was pretty sure he always would.