If you're staying off-site and didn't buy your tickets through Disney, you don't get anything. Zip, zilch, nada.
Yep. And, I think this is probably a big majority of visitors to WDW (and many won't buy tickets until they arrive). I'm sure many people treat a Disney vacation much like other vacations. They go somewhere, probably make some sort of hotel reservation, and figure out the rest once they're there. Even if they read up, it'll be more about "here's the fun stuff to do" rather than "here's what you have to do if you want to plan out your trip."
My parents live in a big tourist area (Sevierville/Pigeon Forge/Gatlinburg) - many people plan week-long trips there, and a LOT of people go there. Other than sometimes booking certain types of lodging (like some cabins) at the busiest times of year ahead of time, there's almost nothing you need to book ahead of time. You can almost always find several hotels in the area, even if you haven't made advance reservations. You can go to restaurants and have reasonable waits. You can do pretty much any outdoor activity by showing up day-of (or maybe making a reservation a little ahead, for some whitewater trips). You can go to the amusement park (Dollywood) with no advance reservations or plans (though they will sell you a front-of-line thing). Most of the shows in town will have many day-of tickets available, and you can often go last-minute. There are numerous mini-golf and tourist-trap attractions around - no reservations necessary. Many people are used to traveling this way - other than maybe a hotel reservation, they don't need to plan much of anything ahead of time. Sure, planning might make their vacation run a little more efficiently ("rope drop" at Dollywood lets you get more done there, too), but it's hardly necessary, and lack of planning is almost certainly not going to keep them from doing any of the things they most want to. If I told people I was planning a trip there and had planned what I'd do each day, I can easily see them saying "we prefer to wing it" and (rightfully) think that I was just overplanning.
So, it's easy to see them saying "this year we'll go to Orlando and see Disney" in the same way, and for the most part that's fine. The restaurants outside of Disney don't require booking way in advance (maybe some of the most popular ones will have long waits, but there are MANY other options that don't). The various attractions on I-drive and 192 don't require advance reservations. You can go to Sea World or Universal and don't have to have made advance reservations, buy advance tickets, or anything else. They might even think it's easier in Orlando, since most hotels will have shuttles to the parks. Maybe they realize they could save a small amount per ticket by buying some things in advance, but it's not needed, and most are willing to pay that little bit more so they aren't locked in to something. So, they show up at Disney, buy their tickets there - and they find they are facing huge lines, can't get into restaurants if they want to (though to be fair, many people will be fine with counter service), and don't know all the intricacies of what it takes to get fastpasses. I'm really at a loss as to why you would expect the average person to think they needed to plan so much ahead of time, when almost nothing else requires that much planning.
I'll admit, if you are staying on Disney property, you do get more warning, though it's still not made clear just how critical it is to plan ahead. Where I live (not a tourist area), several restaurants do take reservations, but almost none
require them, except at really busy times like graduation (or for very large parties). Telling me "you can make reservations 6 months ahead of time" is utterly meaningless, and I can't imagine why I would do so, much less that I might need to do so right at that 6 month mark. Again, it is no surprise that people don't realize they have to make reservations that far ahead - I would think someone was nuts if they started reserving restaurants weeks in advance around here, even when they could. There's nothing abnormal in going up to a restaurant to ask about the wait - who would think they'd be told "you had to do reserve months ago." I especially feel sorry for those who get the dining plan, thinking that has "solved" their dining issues (when in reality, it's probably made them worse if they don't reserve ahead of time, since they are paying for meals they might not be able to use). Once you know the situation, you can look at what Disney sent and say - oh, now I see why they were saying that," but it seems reasonable that people don't really understand ahead of time.