I was a hotel Revenue Manager for a little over 8 years across two different properties. I don't think I've ever heard of a hotel doing this as a conscious strategy. Some speculation:

• By not having rates, the hotel might be hoping that their competitors fill up with lower rates before opening their hotel to bookings. (I think this is unlikely, as having the hotel "open" at rack rates would accomplish the same thing while still allowing people only willing to stay there to book at the higher rates.)
• Perhaps a local company owns multiple hotels and they want to fill up other hotels first. If those other hotels rarely sell out and this one always does, this strategy might make some sense.
• The hotel is in the process of being sold and/or re-flagged. In that scenario, having no reservations made with Marriott points would mean less hassle when the ownership/brand is changed.
• Or, the hotel simply has their settings incorrect.

Of those, I think the last two are the most likely.

At the risk of pointing out the obvious, have you called and asked someone at the hotel. You probably won't find out the rationale behind the odd situation, you will at least find out if it's intentional.