The short answer: I (and my family), like the bus service, and it's convenience outweighs the drawbacks.
The long answer: I can remember on our trips prior to 2010 we always used to rent a car at MCO... and just leave it sit in the resort parking lot all week. There was a time when there was a charge for using the Magical Express bus service. I want to say it was something like $40 or $50 per person. For our (then) party of 5, that was $200 or $250. At that time I had a good friend that worked for a car rental company, so we used his family discount and could rent a nice midsized car for the entire week for around $100. No brainer even with the cost of tolls, fuel, etc. Once on the property, the car would (usually) stay parked. We either didn't use a dining plan, or there wasn't one offered. So on our way in to the resort from MCO we would hit the Walmart (usually in Kissammee) for a cheap $3 styrofoam cooler and some basics for breakfast (cereal, donuts, milk, juice, etc). We would use the resort buses to the parks though.
Now skip forward to our recent trips. DME is included in most, if not all, packages that involve air travel. And even with a discount, I'd be hard pressed to rent a car for the week for $100 lol. So we have no real reason to rent a car. We don't have to deal with our luggage, and we get a nice relaxing ride to the resort. No hassle standing in line at the car rental counter then finding the car, no waiting on luggage, no dealing with traffic and tolls to the property, no fuel stops. I personally don't mind the resort bus service. In general our experiences have been routine and rarely bad. I have to agree with a previous poster - I like the 'down' time on the trip back to the resort at the end of a long day. Helps me shut down for a good night's rest. And I'm getting a little long in the tooth... so convenience is the order of the day when on vacation! So what if it takes and extra 10/15/20 mins over driving. We don't travel with any children, so that makes the decision a little easier lol.
If we lived close enough to warrant driving our own vehicle to Disney, it might be a different story. At least for visiting other resorts as that can be a pain by bus service. Thank goodness there is Uber now... lol! Can't wait to use Uber for our ADR at Sanaa at the Animal Kingdom Villas. Will cut down our travel time for dinner about 2 hours!
Now for a commentary on Disney World's management team opting to include the DME with resort packages - I find this brilliant. Having worked in the amusement park industry, I can truly appreciate the impact of that decision. Here is why I think it was a brilliant move:
1. It keeps people on the property. This is the big one! Instead of shopping or dining off property, most people will opt to shop/eat at Disney and not hassle with a cab (though that attitude might change now with Uber). That alone offsets the cost of offering the DME for free (or at least removing the option for having to pay for it). With the Resort bus service, there really isn't a need for a vehicle of your own.
2. Reduced traffic on the property. As they add more and more resorts & vacation club properties, anything they can do to reduce traffic helps.
3. Reduced wear and tear on the infrastructure. Sure, not a reason by itself, but it does have an impact. I would conservatively guess it easily reduced road traffic on the property by 25%. How much better would the streets in your hometown fare if there was a 25% reduction in traffic? The cost of upkeep and repairs? The 2 times we stayed at POFQ, the parking lots were never 1/2 full. Yet the resort was at 80% capacity. 10 or so years ago the resort lots were full of rentals lol.
Just my thoughts. Hadn't rambled in a while, so felt the urge lol