Why bother?

I've had this debate with many people, of both sexes and all different relationship statuses and am still undecided. After a random hookup (of varying degrees), should a guy ask for your number even if he has no intention of using it? If they ask for it, you sit by the phone (or, in the modern age, constantly checking for missed calls). No one enjoys this...But if they don't ask for it at all, it means that even in their hungover stupor they realize they have no interest in ever talking to you again. This can be quite the ego blow. One way around this is for you to be the one who aquires a number the next morning, placing the ball in your court. But then you have to call, and run the risk of knowing some hit the ignore button when they saw your number pop up. The pitfalls of Caller ID. Maybe the solution is to avoid all of this, not by avoiding random hookups, but by escaping before the other person wakes up the next morning.
Case in point: After going home with the bartender from my all-time favorite bar (word of advice: NEVER DO THIS) he drove me to the subway the next morning. He offered his number, I declined. This was partially cuz I knew where to find him, but also because I knew neither of us planned on this going anywhere. He seemed hurt, and I said if he really cared he could take mine. So he did (Sidebar: he also asked how to spell my name, months later I discover its because he forgot it. Great trick boys, unless her name is Sarah, Jen, etc.) But did he ever call....no. So, why did he bother?