They absolutely do.
1- It's cheaper to have repeat customers than it is to get new ones.
2- As millennials tend to have fewer kids than previous generations (and for zoomers it's likely to be the same, as the factors owing to millennials having fewer kids are still around), soon, Disney will reach a point that there just aren't as many families interested in a WDW vacation.
Disney's been smart by offering cheaper ways to "buy" into Disney (D23, Disney+), and buying IP to expand the company's appeal to new customers - but the parks are still the cash cow.