When I arrange comped rooms with my host, I actually do not need to provide a credit card (although I guess they could root around my past charges and find the numbers). But I have never "no showed" and given the cancellation deadline of 6:00 PM of the day of check-in, any no show would just be rude. I wonder if there is a significant amount of comped no shows enough to trigger this new policy.

It reminds me of Southwest Airlines. Southwest has a company policy that one can reuse fares for up to 12 months with no rescheduling fee. About 2 years ago, a policy was implemented that for discounted fares, one had to cancel at least 10 minutes before the flight or the discount fare would disappear and could not be resued. I imagine this was because a lot of passengers just "no showed" which made Southwest's planning difficult.