My PTO is very generous, so the short answer is I do go other places along with WDW, though lately we've been sticking to the familiar because of the pandemic; this is a record WDW trip year for us just because we've felt safer there.
I still live with my parents thanks to the pandemic (and living in a high housing cost area) and my dad is a DVC member, so actually, going to Disney is not terribly expensive for me (I know a bunch of people's heads just exploded). I pay for airfare, food, and my pass; I don't have to pay for a hotel room, and I get the DVC pass rate. And since Southwest has a hub out of BWI, I have their credit card so I don't have to pay for as many flights, and the ones I pay for are cheap. Plus, my friends don't get as much PTO as I do, so I can go on more vacations, so basically, I can choose to go with my parents or I can choose to stay home. And since they invested in the DVC membership back in 1998, they're going to be doing a lot of Disney.
Plus, for me at least, I can't fully relax in someplace unfamiliar. I went to Hawaii in 2019 and while it was lovely, I wasn't as relaxed as I am in Disney because it's not familiar enough for me. It's almost like when I travel to new places, I need a vacation from my vacation.
And as for why else my family still chooses WDW, my brother is on the autism spectrum and values routine, and going there is part of his routine.
So many, many reasons, but again, I do go other places. I'm hoping to go to California and do some additional exploring beyond DL next year (I've been to San Diego but haven't explored LA much) and I'd like to go to Savannah while I'm in Hilton Head in December since I've never been, along with going back to Williamsburg next year to do Busch Gardens which I've never done.