If Joanie didn't even know what she wanted, then how was he supposed to know? How could he give her what she wanted if she didn't tell him, or realize that she even was a human being with wants and needs like anyone else? And he asked her first because she had to recognize that a relationship - if that was what this was going to be - was not about just what he wanted. It had to be mutually beneficial.
"It's okay to tell me what you're thinking," he said. "I want you to, because I can't read your mind. So do you want to keep seeing me?" Sam asked. "Because I don't want to see anyone else, if that's what you want."