At first thought, it does appear to me as ridiculous that a hotel would not want to keep a waiting list for its best (or any customers). But on futher thought, its probably a lot of work locally and not in their best interest to do so.

I used to negotiate room blocks for conventions and there are commitment release dates usually at 8, 4 and 2 weeks out. So close in, its up to the individual registrant to manage his own reservation.

If a chain hotel is "completely sold out", they are probably sold to 102%, 103% (some number greater than 100%) to account for last minute cancellations and no shows. So there is no great incentive for them to manually manage a list and keep checking the inventory every few minutes day of arrival to see any online cancellations (especially during the 3 pm and onward check in rush hours) which could very well already be replaced by online reservations instantly.

I agree it would be extraordinary customer service to create a wait and notify list for its best customers but I don't see that happening voluntarily (e.g. unless some corporate directive). A hotel that's sold out as of the day before is probably going to stay sold out with some last minute shuffling of the guest names without the hotel's heavy involvement as they inch towards 100%. Plus factor in some walk-up requests in the evening.

Just my 2 cents, as posted above, I've been a "victim" of a phantom waiting list a few times before.