I suspect that the cost of ME was not fully charged to the hotel budgets, but instead was subsidized by other units within WDW. It was originally designed as part of a three-pronged strategy* to create a more captive audience among WDW guests, preventing non-Disney businesses from siphoning off guest attention and spending after Guests arrived in Orlando. The idea was that Guests without cars spend a larger fraction of their time within WDW's borders, and therefore a larger fraction of their vacation's dining and entertainment spend goes to Disney.
Disney has since decided that ME is no longer delivering what it was intended to deliver, and so it is being discontinued. I can think of a couple of potential reasons for that. Ride sharing services (Uber, Lyft, etc.) have significantly reduced the "friction" of getting offsite without your own car. The Resorts now charge for parking**, disincentivizing car rentals with the stick of a daily charge rather than the carrot of ME.
If my suspicion is true, continuing an ME-like service for DVC Members would cause Dues to go up, because the service would no longer be subsidized. Worse, Mears likely offered an attractive rate due to economies of scale, and a DVC-only rate would probably be less attractive because DVC hosts only a fraction of the Guests Resort-wide.
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*: The other two were the Dining Plan (offering a discount to those committing to eating all their meals in Disney restaurants0 and the MYW Ticketing structure (offering a sharp discount for theme park days after about the 3rd or 4th). Both were introduced as the same time as ME.
**: I suspect the parking charges were designed to bias the mix of Resort guests more heavily in favor of fly-to Guests and away from drive-to Guests. At the time, hotel occupancy was in the low 90s, with significant unmet demand. If I was able to pick between a guest that drove their own car vs. one that flew to Orlando, I would probably want the fly-to Guest because they have fewer options for leaving property. But, once the parking charges were in place, it made ME at least partly redundant.