Tombo-
You'd probably be shocked, but over the past 2 years I have seen several posts from people who have done just what you are sure no one would- raised their accepted offer because they wanted the property and didn't want Marriott to nab it. I'd agree that isn't the majority, but it does happen.
I belong in the camp of those who feel ROFR, while certainly good for Marriott, is also good for owners. You are right- it doesn't help sellers, but owners overall benefit from the potential perception of a depressed market because of a few desperate sellers who will let their units go for below market values (and, I know, you will counter-argue that if that's what they went for, that's the market value. However, just like when stores have liquidation sales, the prices they have sold merchandise at doesn't necessarily reflect the true market value).
If you ever have to sell your week for health or financial reasons you will see why owners are listing their weeks for sale for "below market value". Some Marriott owners feel like their weeks are worth a lot more than they actually are worth, and they get upset when someone lists their week for sale for a price that might actually sell. Stores don't liquidate merchandise that is selling well at retail prices, stores liquidate inventory that isn't selling and is costing them money to keep in inventory. Timeshare sellers are the same, prices aren't lowered unless an owner can't be found at current prices.
Go to redweek and pick 2 or 3 different Marriott resorts to watch. Print off the prices of all of those units for sale and see how many sell in 6 months. See how many owners lower their prices after receiving no offers. See how many weeks still don't sell after lowering their prices. It will enlighten you to how hard it is to sell weeks resale for any price, and how long it might take to sell your week if you ever need to.
The simple fact is that if you have a silver ocean view week for sale for $6000 and someone else has the same type week for sale for $5500, no buyer will ever buy yours until that week is gone. Of course many Marriott owners think the problem is the guy selling for $5500. Nope, the problem is that the week for sale for $5500 isn't selling meaning that he hasn't lowered his price enough yet. The other 15 owners with identical weeks realize that no one will buy at $5500, so some lower to $5000. If months later no one has bought it goes to $4500. When sellers find a price that will sell the market value has been reached and a sale actually occurs. Until then the ads are never going to produce a buyer. Many owners drop their prices numerous times hoping to find a buyer. Of course ROFR is getting them a good price (sure it is) so they really don't have to drop their price. They could hold out for the great ROFR price, but they instead choose to drop their prices because as we all know the goal of all sellers is to sell their week for as low of a price as they can get. These bad owners always remember to buy high and sell low.
If Marriott wants to really prop up prices they should buy all the weeks for sale at $6000 or less and then none will sell for less than $6000. Until Marriott starts to actually buy back weeks (which they will never do) then weeks will sell for whatever the market will bear. ROFR hasn't helped a thing.
Many owners here refuse to sell their weeks for those "below market" prices, so they list them for sale for a high price secure in the knowledge that thanks to ROFR a magical buyer will appear. This magical, ROFR educated buyer will simply call them and offer to pay them more than he could buy 15 identical weeks from other sellers for. The owners who refuse to sell their weeks for "below market prices" in reality simply refuse to sell their weeks. They will own them as long as they keep telling themselves that ROFR will get them a buyer at a higher price than a real buyer will pay.