In your hotel example, you should look at the WTP for a room. I might pay $150 for a room, and up to $250 for the high end room. So even if the sticker price is $500, it's value to me is closer to $250, so I'll calculate my CPM that way.
Just like if Amazon offered me a year of prime membership for $10 I'd say "no thank you" because I value prime membership at $0. (Don't shop at Amazon much, don't mind waiting for shipping, have all the streaming I need)
Even considering you can book rooms for others, there's still a huge segment of the population (50%?) where hotel points are still completely useless. There's a time in my life hotel points would be completely useless to me too. Many people don't travel and don't have friends/family who travel either, it's as simple as that. The HN crowd seems to believe that everyone is taking a few vacations to far away places a year but that's simply not the case, most people I know do not travel at all and do not want to either.
Plus, even you wanted to use them they would have to have a hotel at the destination where you also wanted to travel to.
You can get a $500 hotel on points. You don't say "well, I live for free at home, so technically this night is worth nothing."
Just because you can "buy" something with a different currency that might make more sense, doesn't make it cost less in USD if you were to purchase it outright.