Thank you. I've heard that, but it's hard to wrap my head around that reason. The dining plan is simply a payment method and as we generally have to make dining reservations, all that matters is being able to show up and eat then pay. People in the parks will still need to eat, dining plan or not. Staffing wouldn't change if reservations or availability is limited, which, frankly, has always been the case due to the number of tabletops in a restaurant. Why not let us pre-pay and enjoy a simple trip?
Yes, I know people will want to make reservations if they have the plan and be frustrated if they can't find availability during certain times, but it's not like anyone could eat anywhere desired at the drop of a hat before. Having a dining plan did not = reservations. We've always needed to book well in advance to "guarantee" a table or deal with the frustration of not getting desirable reservations (or any, to be truthful) because they're already "sold out."
The above is directed at Disney, not you.