I don't think there really is a "rule". The polite thing is obviously for him to have say I had a great time but i don't see this leading anywhere but it seems some people just like to let things peter out. I don't date much (or at all lately) but from boards I hang out on this question comes up a lot more lately.

I think some people are afraid of rejecting other people. Of seeming harsh or hard. Not wanting to hurt the other person so they try to ignore the whole thing and hope the person gets the message. I know I struggle with finding the words when I'm just not into that person. I tend to lean towards proper etiquette being to tell the person so they can move on and focus on finding something else.

Sorry it didn't (or appears to not) work out for you. Here's to other fish in the sea
Robin