Of course there is some benefit.
1) Increased dollars spent on-site by resale members year after year, tickets, food, merchandise.
2) Potential future direct sales. You assume that no resale owner has ever purchased direct add-ons or new contracts at new
DVC resorts.
3) Referrals. Happy DVC owners are their best advocate for generating new sales.
4) A reason for their captive DVC audience to keep returning to Disney for decades to come.
5) Cross-selling. DVC members are more likely to be open to purchase other Disney products, like cruises or travel experiences.
6) At any time they believe a resale buyer is getting TOO GOOD OF A DEAL. They have right of first refusal. They can take that resale away from the buyer. So, all this talk about how resale owners are some how hurting direct owners - blame DVD, they can buy up every single contract. Obviously they don't want to do that. It's a symbiotic relationship. They need resale customers to keep values high. Additional restrictions will decrease resale value thereby hurting direct purchasers the most.
If any direct purchasers are worried about their yearly vacation, then perhaps a fixed week option will provide them with the peace of mind they want. However, I would never opt for a fixed week, I would venture to guess that most people don't vacation that way.