Definitely not required. But it is very nice. Discounts on food and merch are good, though you can get a lot of those with the visa card too.
Once you have a lot of points annual passes are pretty much a given. We have saved around 2k ish on annual passes by getting the
DVC sorcerer pass just the last 2 years already even with just the 2 of us. That would be 4k if we were a family of 4 so the savings can definitely add up, especially with larger families.
And we have some gotten discounts on after hours parties, halloween parties, christmas parties etc too. And used the lounges on occasion too.
And we know we can use at least part of our points at future resorts if they come up with some cool resorts in the future that we want to try but not necessarily buy into. Definitely a lot of things to think about with a direct purchase.