As far as the Park Reservations point goes, I believe that 'Crowd Control' was the initial driving force.

With the number of people visiting since CoVID restrictions were lifted, some parks 'sell out' of reservations from time to time. It is best to make your reservations as quickly and early as possible so as not to be 'shut out' of a park on any particular day. You can check reservation availability here:
https://disneyworld.disney.go.com/av...egment=tickets

Hope this helps.