"Wanna come **** me?" "Err...what are the benefits?"

Some people are just completely oblivious about flirting, doesn't mean they don't know about sex. Besides, it may be all a show because his dad is right there! It's awkward.

maybe he's just not interested in her. you know not all guys want to just **** everything. if your son had standards be proud.

Heaven forbid your son have standards. Maybe he just didn't see anything of interest in her or thought she was too easy, maybe he already has his sights on someone else, maybe he didn't want to accept a one night stand in front of... you know... DAD. Awkward. Then again, you took him out to go shopping for stuff, not women, right? maybe he's just super goal-oriented and didn't want to focus on anything else.

Maybe he's gay?

So your son didn't get laid today, and that means you've failed as a father? Yes, you really have if that's your outlook on things.

I have to admit I was totally oblivious in High School. If the OP son is in High School maybe a good thing. In college though one would hope the kid is at least more aware. If he's that unaware it could definitely prevent him from meeting someone in the future. Also, if he's that unaware it is possible he may need instruction in social skills. Those that are bad with signals generally also have other social issues that might negatively impact them from also making friends.

Good for your son. You only fail as a father when you think it's appropriate for a girl to ask a strange guy that's she's never met to go back to her place with her.

.... maybe he wasn't into her? Maybe he was worried about more important things?

"He'll do it."

Or he could be not interested?

Get a number mate?