I have to say that this is one topic that I'm on the fence about. I have been regularly going to WDW since February 1983 and never once have I brought food or drink in with me. I do know many that did that, however. I don't think it is necessary (other then medical), but, it would be nice if Disney were a little more reasonable concerning their food prices. Sadly, they aren't and are not likely to ever be again. I guess when you figure how much it's already costing to have a Disney Vacation that is a small part of it. Reasonable means different things to different people though. I stay offsite so two of my meals are a going to be at a fairly good price anyway. That leaves lunch and snacks. So, like I said... doesn't mean anything to me at all.
I hate to say it this way, but, really people need to budget the cost of food when they go there. Plan for it and make sure that they can afford it before they go.
It does represent a difference in some of the people that will be able to attend. I remember back in the 90's witnessing a crowd of, I'm assuming, family members during what was called "Florida Day" when admission to the park for Florida residents was something like half price, going from person to person collecting change to buy a single fountain drink that was then shared among a number of people in the group.