Generally I think it's because the fanbase is on the younger side (?) (not really an excuse I mean I was 13 when I read these for the first time) but a lot of people seem to really not understand David Eastman as a character.
Yes, the spoiled rich boy archetype is very popular right now - but that is not who David is. David is a victim of neglect and emotional abuse from a man who happen to be rich and his alcoholic mother who was also taken advantage by a man who happens to be rich. Edward King being rich is important to the way his character functions (he's Donald Trump), but David having money is basically inconsequential to his character besides in how it changes Stevie's view of him.
Stevie is an unreliable narrator, she's also a teenage girl - she's very blatant about not understanding things. It's up to the reader to read between the lines. She thinks about David being rich kind of a lot, because money is a pretty big part of her life. But David - what, he buys the Sherlock coat and he doesn't get expelled. That's basically it. He gets offered university cash in book 4 and doesn't even take it.
And David like a political terrorist, for the record, he isn't spoiled or morally bankrupt due to his connection to King, he hates the guy (as one would, again, Trump). He sabotages his political campaign and goes on the road. That's Cool and Sick.
He's sort of a dick to Stevie, this is true. Stevie also likes it. David is a challenge and that what Stevie needs. If we're going to dislike they're relationship really it's more about Stevie crossing his boundaries than he crossing hers. People seem to forgive the whole going through his computer thing because she was right, but David was trying to keep that a secret for a reason. Ellie was the only person he told, his dead best friend.
David isn't always kind - but she's always trying to do the right thing. He goes to lunch to Stevie's parents, he saw a problem and knew how to fix it. Stevie wasn't pleased but she was still At Ellingham after it all. Objective complete.
He didn't give her a iPad, he followed her in the snow, he took the fall after finding Ellie's body so Stevie wouldn't get in trouble.
A lot of this changes in Nine Liars, and hoping Maureen doesn't change his characterization in book 6 because I Really Like It.
